Now. From nbc news World Headquarters in new york. This is nbc nightly news. Reporting tonight lester holt. Good evening. As we begin here tonight, Severe Weather is breaking out in several states across the south. Tornado watches and warnings are up from dallas to southeast louisiana, where a storm blew 18 wheelers on their side. All signs point to a dangerous night and weekend ahead for at least 13 states. Were entering what is anticipated to be a multiday event of violent storms. Will bring lightning, hail and as many as two dozen tornados. E are seeing a very volatile situation right now. Were watching strong storms approaching louisiana. In new orleans, 8,000 lightning strikes in less than ten minutes. The areas in yellow tornado watches, in red, tornado warnings. Kansas in fact hutchinson, kansas. Were looking at the risk of severe storms. 32 Million People at risk. This danger continues into saturday and mos to the east. Charlotte, atlanta, st. Louis. 32 million folks at risk for severe storms large hashlgs damaging winds, torrential rain. Th moves into sunday as well. Again, the same area. Oklahoma city dallas into san antonio. 16 million folks at risk. And we have flash flooding possibilities anywhere from three five inches from arkansas down into louisiana. Is going to continue right into next week. So flooding and a lot of damage expected this weekend. Now to a terrifying scene on camera. Dozens of students d on a stage, dancing and singin a school near indianapolis when the stag collapsed sending students ti to the pit below. Reporter it wasnt the big finish to the show of 80s music the students had planned. Singing turned into screams as performers plunged 12 feet to the concrete floor of an empty orchestra pit when a temporary stage gave way in front of a packed auditorium. People were crying running up to the stage trying to help people out. Reporter 16 were treated for broken bones, the torn ligaments and possible concussions. Pretty sure no one in a million years thought this would ever happen. Reporter singer nicole griska had just stepped off before it collapsed. When you looked down w did you see . I dont remember frankly, because i immediately started crying. I remember hearing them screaming, which, and hearing people say help me which was, just terrible. Reporter musician omar santiago was the enthusiastic young man in the spotlight. It was instant. One moment im celebrating. Next thing i know im in the hole. Reporter today federal, state and local officials are investigating, looking at the schools maintenance records. We all want the same answers. The Community Wants the answers. We want to make sure this never happens again here or anywhere. Reporter classes were held today but attendance was optional. We all hugged. It was good to see each other again. Reporter after a night that few will soon forget. Westfield, indiana. Tonight, baltimores mayor and Community Leaders are pleading for c e c prepares for what may be its most massive protest yet over the death of a man who suffered a serious injury while in police custody. And the commissioner is admitting to serious mistakes by his officer, including not providing timely medical treatment. Reporter today confirmation from Baltimore Police that freddie gray was arrested and placed into a police van, arresting officers failed to put a seat belt on him a violation of police policy. Know he was not buckled in the transportation wagon he should have been. No excuses for that period. Repor also police sai appeared to be talking and moving in the van until the third stop. Among the questions, was gray given as whats known a rough ride jarring stops and starts that might have caused his fatal injury. If someone harmed freddie gray were going to have to prosecute them. So giving too much information on the front end may jeop that prosecution. Repor demonstrators have answer. Among the protesters entire families including 11yearold david williams. Im worrying about me dying. And im thinking of everybody in my neighborhood stressed out with crack. I dont want to die. Reporter now they are promising to ratchets up the pressure tomorrow. They want an end to the cycle of black men being shot down gunned down having their spines broken and backs broken. The people of baltimore are demanding this. Reporter but today, surrounded by civic and religious leaders, the mayor urged all protesters to remain peaceful. This community and this whole community is committed to seeking justice for mr. Gray. So if youre going to come here come to help us not to hurt us. Reporter baltimore are also asking for witnesses to come forward. By the way, five of the six officers have now voluntarily talked to investigators. One has not. And the Baltimore Sun reports that over the past decade two suspects have won court case against the city for being paralyzed while riding in those police vans. Tom costello in baltimore, thank you. Overseas a stark reminder of the growing Terror Threat that hangs over so many countries. Today a series of raids in italy resulted in arrests in a Terror Network that had once plotted an attack on the vatican and the previous pope himself. Richard engle has the details. R the target of terror reportedly pope ben dibts himself. A plot totarget the vatican by a major Al Qaedalinked cell. They were broken up and recorded on police video. 18 arrest warrants nine detained and nine still at large. The suspects are pakistanis and afghans. A key figure prosecutors say, this preacher arrested outside milan. It was a fundraising cell for al qaeda in pakistan investigators say, in direct contact with osama bin ladens inner circle. Italy has been following this group for years, recording their phone calls. Thats how the 2010 plot against the pope was finally uncovered. This is a series of guys that were involved in a plot sometime back. Reporter italy these days is on edge. And its not alone. Since the paris terror attacks in january, there have been dozens of police raids across europe. France germany, Great Britain and italy, with fears of terrorism, anger and antiimmigration se are growing. And now in italy theres more concern than ever with migrants arriving by the thousands every week on boats from libya. Italian politicians warn that among them could be militants from isis which has repeatedly threatened to attack rome. The vatican is downplaying the threat saying there was no specific cause for alarm. And today, a cardinal sa the current pope francis is quote, calm and serene about his security. Ew revelations tonight t the cia drone strike that mistakenly killed two whosages. One of them an american while president obama is reinforcing his faith in the nations spy agencies just one day after apologizing for that botched operation. Nbc Chris Jansing has more. Reporter p got a standing ovation today from members of the Intelligence Community and a hug from james clapper. One day after revealing that a cia drone strike accidently killed warren weinstein. We all bleed when we lose an american life. We all grieve when any innocent life is taken. Rep nbc news has confirmed that when u. S. Drones struck an al qaeda compou to hit four terrorists but found six bodies. It would be weeks before they could confirm weinstein and an italian hostage had been there two. Weinsteins widow thanks italian Prime Minister for his koncon condolen message a phone call from president obama. Her congressman has called for the creation of a hostage czar to create efforts to coordinate for hostages. Its a government bureaucracy. Its not an academic exercise. While the state department wont release ebs act numbers, at least six americans are believed to be held oversees including Kaitlyn Coleman who was pregnant when she was captured in afghan in 2012. In iran amir heck mattie and levinson. Today the white house said it is considering something similar to a hostage czar but wont change its policy of not negotiating with terrorists. Sos a t y is used in these situations and late today, sources told nbc news thats how they were able to get warm clothes to weinstein during captivity. A somber 100th anniversary marked what pope francis called the greatest genocide in the century. Observances in armenia, throughout europe the middle east and here at home where tens of thousands marched through a Los Angeles Neighborhood known as little armenia to the turkish consulate, waving signs and flags to make sure the world never forgets. Angelina jolie brought her star power to bring attention to the humanitarian crisis in syria. She did not mince words, accusing the u. N. Of not doing enough to help the millions who have fled the country or been displaced. We cannot look at syria and the evil that has arisen from the ashes of indecision and think this is not the lowest point in the worlds inability to protect and defend the innocent. Jolie is a special envoy. When asked about her briefing syrias ambassador is quoted as saying shes beautiful. There is an alert tonight about a growing outbreak of bird flueing through the u. S. Poultry industry. 7 million chickens and turkeys affected since march. And the government is scrambling to figure ouw to stop it. Nbcs Janet Shamlien has our report. Reporter the most significant bird flu outbreak in 30 years. Minnesota the latest to declare a state of emergency. Tonight more protective measures, disineffecting ve and farms. This man has 300,000 chickens. Some of them are sick. I know what a healthy bird looks like. And the looked a little bit sick. Reporter his farm now under quarantine. And a complete lockdown at sun rise farms in iowa one of the largest eggproducing plants in the nation. The entire flock will be lost almost 4 million hens. Thats more than 1 of the egglaying hens in the u. S. Its pretty serious right now with the number of cases were seeing and that were still continuing to see on a daily basis. Reporter the highly contagious avian flu has spread to 16 states calling it the biggest outbreak ever. Disease spread through th droppings offing my rating birds can be fatal within 48 hours. Maryann runs blue star farms in texas. One of the many whose birds are now healthy. The avian flu is definitely something be concerned about. We do our absolute best. The the cdc says the risk in humans is low. Mexico russia and more than 50 other countries refuse poultry from affected states. Our food supply is safe. The fda says theres been no infected powell fry or eggsconsumers. A growing catastrophe no the heart the heartland. 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