A mob boss in front of his home. The messages he scrawled on his hands flashing them for the cameras to see. A big reversal from doctors about that daily dose of aspirin in preventing heart attacks. What everyone watching should hear. A stunning new turn in the case of a violent shove caught on camera. The teenager seen pushing her friend off a bridge, plunging 60 feet below. A Police Officer dragged down the street in a swarm of atvs. Tonight, the hunt for the driver amid a growing nuisance in cities around the country. The young chess champ beating the odds and inspiring america. Tonight, has one of the worlds most infamous mysteries finally been solved . his is nb nightly news with lester holt. Good evening and welcome to our viewers in the west. Were following two dangerous situations developing as we come on the air tonight. A raging inferno in houston, and the massive flooding in nebraska that has left entire communities cut off. Well go there in a moment. But unfolding, as we say, that pet rowchemical fire just outside houston now in its second day, spewing a dangerous tower of black smoke tonight visible for miles. More than a half dozen storage tanks have caught fire and authorities are monitoring air quality. Our Gabe Gutierrez is there with the latest. Ive seen nothing like this for this long. Ever. Reporter tonight, this massive fire at a petrochemical plant near houston is still raging after spreading to seven storage tanks. Thick, black smoke billowing for miles. This is the worst ive seen in the last 12 years. Reporter the blaze started sunday morning, then it spread overnight. The tanks were filled with chemicals used in gasoline, paint thinners, and glues that problems, and skin irritation. Authorities now saying it could take two more days to douse the flames. Rg to work with foam and water to control and prevent the fire from spreading. Reporter still, they lifted a shelter in place order for the town of deer park, texas, and say its safe. We continue monitoring the air quality in and around the areas in several locations. As of this time, theyre still within normal range. Reporter its not clear how the fire started. No injuries have been reported. As a precaution, schools in the area were closed today. Residents like Michael Comber are on high alert. Everything out there is under pressure. Its got gasoline and, along with it, other chemicals. Reporter Public HealthOfficials Say the plume is high enough off the ground so that its not affecting us here, but local Authorities Say they are monitoring wind conditions very carefully and are on standby in case this smoke descends. Lester . Dangerous and dramatic background there, gabe, thank you. Another emergency were following tonight, the historic Flood Disaster in the midwest and plains. At least three people are dead, 10 million are under flood warnings and advisories. Nbcs kathy park is in hardhit fremont, nebraska, northwest of omaha. Reporter recordhigh rivers turn small, midwest towns into islands. Offutt air force base near omaha under feet of water. Entire parking lots submerged. In nebraska, extreme flooding cut off communities across the state as the water raced in. Some homeowners have been stranded for days. I cant believe how much water came in. Its insane. Reporter heavy rain and significant snow melt fueled this disaster. The worst the region has seen in decades. Minnesota, wisconsin, iowa, and illinois also hit hard. River gauges there near or above flood stage. National guard soldiers are pulling people and pets to safety. Strangers also pitching in. This is what nebraskans do. We pull up our britches and help each other. Reporter russ zime says the lake is now in his home and the water could take days to recede. The sad thing is the personal memorabilia and family heirlooms and stuff like that. Theyre priceless and cant be replaced. Reporter historic flooding quick to move in, now slow to move out. As the waters here slowly start to recede, states south of the region could be next. River flooding is likely in the coming weeks as the floodwaters head downstream toward the gulf of mexico. Lester . All right, kathy park in nebraska tonight, thank you. This evening nbc news has confirmed a federal investigation is looking at boeing 737 max jet and how it was approved for flight. The max had been the bestselling plane in the world, but as weve been reporting, it was grounded last week after two crashes in five months killed more than 300 people. The question this evening, did the plane get the proper oversight before it was certified to fly . With more on that, heres nbcs tom costello. Reporter with the worlds 737 max fleet grounded, a federal grand jury is investigating the development of the boeing max and how the faa certified it. Understaffed and underfunded, the faa has delegated much of that process to boeing itself under a plan approved by congress. There is always a risk of delegating some of your direct Certification Authority over the aircraft design. But you need the manufacturers expertise. They know their product better than anyone. Reporter online, the faa says the goal of the program is to identify best practices and develop strategies to streamline certification and oversight. I asked the acting faa chief last week about the interaction with boeing. Did your close relationship with boeing and with the airlines in any way lead you to delay the decision to ground these planes . Absolutely not. Reporter meanwhile, french investigators analyzing the black boxes from the ethiopian crash said today clear similarities were noted between the ethiopian and indonesian planes before they crashed. Bad sensors on the plane or a software glitch, and a new antistall system called mcas, is suspected of forcing the indonesian plane down. And possibly the ethiopian airliner too. But pilots werent told about mcas until after the indonesian crash. Then given an ipad course to follow. Before they were grounded, American Airlines pilots stood by the plane, now they want simulator time. We dont want to see another 10 or 15minute ipad course to tell us, heres the differences, now move along and fly. It doesnt work that way. We take this much too seriously. Lester, late this evening, the ceo of boeing released a video statement. Safety is at the core of who we are at boeing. Soon, well release a Software Update for the 737 max that will address concerns discovered if the aftermath of the lion air 610 accident. Meanwhile, can day says they will not rely on the faa to certify pl. Firing back after President Trump unleashed a dayslong tirade against her father, the late senator john mccain. The president continuing to attack him more than six months after he died. We get more from nbcs kristen welker. Reporter tonight, Meghan Mccains blistering rebuke. That tells you everything you need to know about his pathetic life right now. Reporter going after President Trump for his new twitter attacks against her father this weekend. He spends his weekend obsessing over great men because he knows it and i know it and all of you know it, he will never be a great man. My father was his kryptonite in life, his kryptonite in death. Reporter the president s tweets come nearly seven months after senator john mccains death from brain cancer. In one tweet, the president citing former independent counsel ken starr, who blamed a mccain ally for leaking a copy of that unverified steele dossier about mr. Trump and russia. This is unfortunately a very tweeting mccain had r tonight, democrats blasting the tweets. Well, its despicable. John mccain is a hero. Repulsive, repulsive. Reporter the white house on defense. So i will always respect and applaud senator mccains service. I think what the president wants folks to focus on there is just the origins of the dossier. Reporter and another focus for the president . Joe biden and this slip of the tongue. I have the most progressive record of anybody running for the united anybody who would run. Reporter the president tweeting, biden was unable to properly deliver a very simple line about his decision to run for president. Get used to it, another low iq individual. Biden has been hinting publicly about a possible president ial run for weeks, and telling friends that hes all but certain to launch a third president ial bid. Hes expected to make a final decision by next month. Lester . All right, kristen, thank you. Theres a new twist this evening in the killing of a reputed mob boss. Een a mafia hit after all. Police now believe the suspect, who was in court today, may have wanted revenge over a relationship with the victims niece. Heres nbcs anne thompson. Reporter in court today, 24yearold anthony comello, the man police say put 10 bullets into alleged new york mob boss Francesco Franky boy cali. Scribbled on comellos left hand, maga forever, united we stand. Comello nabbed in new jersey along with police say the blue pickup truck used in the crime. Is it true youre waiving your right to extradition . Yes, sir. Reporter waiving extradition to Staten Island where cali was gunned down in front of his home last week. We do not believe this was a random act. Reporter but is it connected to calis role as a leader in the gambino crime family . Tonight, Law Enforcement sources say comello was angry he was told by cali to stop seeing his niece. What ended in calis death began with comello ramming his truck into calis parked, was he acting alone . Was he acting for other people . Are there others involved . What is the motive . I simply, standing here, do not have all those answers for you. Reporter comellos Attorney Says his family has no answers either, promising in a statement, there is something very wrong here, and we will get to the bottom of it. A young man perhaps trying to end one problem now facing so many more. Anne thompson, nbc news, new york. Lets turn overseas now to a deadly attack today in the netherlands. Investigators are trying to determine whether a suspect had an International Terror motive when he opened fire on a tram, killing three people and injuring five. The suspects family in turkey says it was part of a domestic dispute. The suspect was captured after a massive manhunt. New fallout from the deadly terror attacks in new zealand. The Prime Minister vowing to reform that countrys gun laws in just ten days after a gunman killed 50 people at two mosques. Our Miguel Almaguer is there with new details for us tonight. Reporter tonight, new accounts of heroism during 36 minutes of terror. Ali adib says his father took a bullet for him. All he said was, take care of your mom and your brother and sister. Reporter abdul aziz came face to face with the shooter, scaring him away after grabbing one of his unloaded guns and chasing him out of the second mosque. I just wanted to take his focus out from the mosque. Reporter but already 50 lives had been taken. The suspect, brenton tarrant, in court, smiling, flashing a white power sign, his face blurred. While shootings of this magnitude in the u. S. , from parkland to las vegas to sandy hook, have sparked debates over what to do about gun violence, tonight new zealands Prime Minister has given a deadline to change gun laws here. Within ten days of this horrific act of terrorism, we will have announced reforms which will, i believe, make our community safer. Reporter its unclear how this country, where many people own guns, will react. Meanwhile, tonight, dozens are still hospitalized. Wasim and his 4yearold daughter are suffering from multiple gunshot wounds. Please pray for myself, for me and for my daughter. Reporter among the victims killed, refugees from syria who survived the civil war. Tonight, nine people remain in critical condition. Lester . All right, Miguel Almaguer outside that memorial, thank you. Back home, Nashville Police are asking for the publics help to find an atv driver caught on camera, dragging a Police Sergeant down the street. Officials warn swarms like these are a growing problem across the country. Lets get more from kerry sanders. Oh my god reporter a nashville Police Officer dragged by an atv along a downtown street. The cop tumbles violently. Police say offroad dirt bikes and atvs swarmed the area with little warning whe john borque, trying to stop one driver, was entangled. Then he just accelerated into him. Reporter from miami, to new york, to philadelphia and now nashville, detectives believe the throngs of offroad riders organize these mob takeovers of urban streets on social media. In nashville, another offroad biker in that horde slammed into a car. Theres a place for atvs and its not the city highways. Its not in front of my church. Reporter tonight, one nashville Police Officer is lucky he wasnt seriously injured. As investigators now try to determine who is this man . Kerry sanders, nbc news. There is Important News tonight about aspirin and heart health. A big reversal from doctors about who should be taking a daily aspirin after new evidence shows the daily pill could actually cause more harm than good. Heres nbc news medical correspondent dr. John torres. Reporter its longstanding advice followed by millions of americans, an aspirin a day can prevent a first heart attack. But now a major aboutface. New guidelines from the American Heart Association now say adults over 70 should not be taking the drug. Aspirin isnt harmless. Reporter the new recommendation comes after three large studies found that aspirin did not prevent heart attacks and strokes in older adults. In fact, taking it every day raised the risk of serious harm like stomach and brain bleeding. Those who should not take aspirin include people over 70, anyone who does not have heart disease, anyone at risk for bleeding. For someone taking aspirin right now, what should they do . People taking aspirin should not just stop. They should have a conversation with their physician and really determine their individual risk versus benefit. Dr. Torres, who should still be on aspirin . People who have already had a heart attack or stroke, for them daily aspirin can be life saving. People at high risk of their first heart attack or stroke should consider the pros and cons of taking aspirin with their doctor, though, before they start taking it. Dr. Torres, thank you. Just ahead, a major reversal this evening in the case of a teen seen on camera, violently shoving a friend off a bridge. Then who was jack the ripper . Has the 130yearold mystery finally been solved . The 8yearold chess champ whose inspiring story you have to see. Stay with us. Stay with us. 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Ooh reporter a violent shove caught on camera, set to be played in court in the case against then 18yearold taylor smith, seen pushing her friend jordan helgerson off a 60foot bridge. This morning, the teen changing her plea to guilty on the day her trial was supposed to begin, admitting to reckless f house arrest, community service, and work crew detail. Jordan says it should have come if she would have pled guilty in the beginning of all of this, it kind of would have showed responsibility. Reporter back in august the video going viral, jordan hospitalized for a punctured lung and broken ribs. It was what happened prior to the shove that was expected to play prominently in the prosecutions case. Taylor heard saying she was going to push jordan. Jordan, im going to push you. No. Reporter video showing jordan shaking with fear. Im so scared right now. Jordan . Go. Go. Reporter at times, others saying jordan didnt want to jump. Well, shes saying no. No. Ready . Ooh reporter jordan says she still has anxiety attacks and hopes, despite the plea deal, the judge sentences her former friend to jail. For the jail time ive spent sitting in a bed in the hospital. That she put me in. Reporter Gadi Schwartz, nbc news. It always remains hard to see. Stop fearing your alarm clock. With zzzquil pure zzzs. A drugfree blend of botanicals with melatonin that supports your Natural Sleep cycle so you can seize the morning. Zzzquil pure zzzs. And youre still not sure if you want to make the trade . Exactly. Alright, call td ameritrades trade desk. They can help gutcheck your strategies and answer all your toughest questions. Call for a strategy gut check with td ameritrade. And relief from symptoms caused by feel the clarity of nondrowsy claritin. Over 200 indoor and outdoor allergens. Like those from buddy. [ dog whimpering ] but i can tell you Liberty Mutual customized my Car Insurance so i only pay for what i need. Oh no, no, no, no, no, no, no. 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Theyve published new evidence taken from a shawl belonging to catherine eddowes, one of five women jack the ripper killed. At the time of the killing spree on these streets, the bloodstained silk shawl found here offered no clues. Now Scientists Say new dna tests link jack the rippers fourth victim clearly to one man. O barber, once a prime suspect. His dna taken from living relatives. Scientists began analyzing it four years ago. Other scientists are skeptical, saying the dna could match many suspects. Tonight, ripper tours are out on the streets. You see the glint, the evil glint of his eyes. Reporter but the mystery of his true identity still lingers. Bill neely, nbc news, london. Next for us tonight, the 8yearold chess prodigy winning trophies and hearts. Dog, the scenery never changes. Thats why this is the view for every other fullsize pickup. 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No. Reporter Tanitoluwa Adewumi is tenacious and smart, and like other good chess players, he simply sees things on the board his opponents do not. What i like most about chess is deep thinking. Reporter deep thinking . Yeah. Really deep. Reporter he handily won the new york state chess tournament in his age group this year, not bad for an 8yearold who only learned to play the game a year ago. His family came to america from nigeria two years ago. Christians fleeing persecution, his dad works two jobs and his mother just passed a Home Health Care course. Where do you live . We live in shelter. Reporter yes, theyre homeless. So one of his coaches started a gofundme page to help out. And as tanis story spread, the money started pouring in. People are good. People want to support them. Reporter the family is overwhelmed, proud of their son who is heading to nationals in may, and stunned by the generosity of a city and country where they prayed to find refuge. Im so proud of him. Reporter like in chess, making the right move can make all the difference. Harry smith, nbc news, new york. Heres some more good news. Weve just learned the gofundme page raised over 100,000, and tanis family is moving into an apartment tomorrow. Thats nightly news for this monday. Im lester holt. For all of us, thank you for watching and good night. Right n fed up with the train noise. The neighborhood in the south bay that s fighting back against late night service. Plus three shootings in three days along our freeways. With the train noise. The neighborhood in the south bay fighting back against late night service. Three shootings in three days along our freeways. S doin gun men. But first a march set to start any minute marking one day since police shot and killed an unarmed black man. The message family and friends want everyone to hear. The news at 6 00 starts right now. Thank you so much for joining us. And im jessica aguirre. Marchers are set to take to the streets of sacramento tonight to remember the death of Stephon Clark. Clark died a year ago exactly today. Tonight though there is a new push for action. Taking center stage civil rights leader reverend al sharpton. That march is supposed to take off in just a little bit. Reporter it looks like it has just started. I want to show you what is happening right now. You can see supporters of the clark family primarily members of the local chapter of the black lives matter are startin they plan to march through the neighborhood where Stephon Clark was shot and killed one year ago. The clark family Breathes New Life into the movement. This case is a national disgrace. Reporter where he goes cameras typically follow