Announcer from nbc news World Headquarters in new york, this is nbc nightly news with brian williams. Good evening. Im lester holt sitting in tonight for brian. Anxious months and months of hope and worry has turned to unimaginable grief today for the family and friends of 26yearold hostage Kayla Mueller. They received the confirmation they had been dreading that kayla is, in fact, dead. Her isis captors first reported her death last week, claiming she died in a Jordanian Air raid but offered no proof at the time leaving her family back in arizona a glimmer of hope. Today president obama said about the young aid worker, how she lived her life, she epitomized all that is good in our world. But it is the written words of kayla herself tonight that tell us who she was and define her remarkable courage. Joe fryer reports from her home town, prescott, arizona. Reporter emotions are strong tonight in Kayla Muellers hometown, a year and a half after she was taken captive by isis relatives say they received a message from her captors confirming her death. Kayla has touched the heart of the world. The world grieves with us. The world mourns with us. The world wants to be more like kayla. And if that is her legacy and the footprint she leaves on the world, then that is a wonderful thing. Reporter u. S. Officials tell nbc news the family received a photograph of mueller that appeared to show her dead with trauma injuries, but its difficult to determine the cause of death. In a statement muellers parents say, our hearts are breaking for our only daughter, but we will continue on in peace, dignity and love for her. Her family also released a letter handwritten by mueller last spring while she was in captivity. I have a lot of fight left inside of me, she wrote. Im not breaking down and i will not give in, no matter how long it takes. I am in solidarity with the syrian people. Reporter 26yearold mueller was working for aid groups along the turkish Syrian Border when she was captured near aleppo in august 2013. In a statement president obama says, no matter how long it takes the United States will find and bring to justice the terrorists who are responsible for kaylas captivity and death. On behalf of the people of arizona and the United States congress i want to express the deepest condolences. We pray for kayla today. Reporter over the weekend in arizona, they prayed for muellers return. Tonight, theyre grieving her loss. She was a fine young lady. Thats for sure. And shes done prescott well. Reporter in muellers letter which was smuggled out by her cellmate, she said at the time she was in a safe location completely unharmed and healthy and being treated with respect. Whats unclear tonight is exactly how she died and when. Joe fryer, thanks. Kayla muellers death follows months of shear horror, journalists and aid workers beheaded, a jordanian military pilot burned alive. Each atrocity bringing new resolve to the fight. President obama is expected to ask congress this week to formally authorize the use of force against isis, though theres a good deal of force being applied already. Our chief Foreign CorrespondentRichard Engel has more for us. Richard, good evening. Reporter good evening, lester. In many ways, the International Coalition against isis has never been stronger. And critically arab allies are now fighting with a renewed enthusiasm. The air strikes are coming harder and faster now, bombing runs by the u. S. Jordan and the United Arab Emirates flying new missions against isis targets in iraq and flying them from jordan showing solidarity after the brutal killing of a jordanian pilot. But isis said the air strikes are not slowing it down and claims they cost american hostage Kayla Mueller her life. Isis says mueller was in this building near raqqa targeted by jordan at the direction of the United States a claim dismissed by the commander of jordans air force in an interview with nbcs keir simmons. We were miles away. Reporter isis also claims the u. S. Is allied with syrian president assad because theyre both bombing isis. In a rare interview, assad hinted to the bbc that the two countries are in touch, though not directly. Theres no dialogue. Theres, lets say, information. But not dialogue. They tell you things . Some things. Do you tell them things . No. Reporter this war is making strange bedfellows. President obama who in 2011 said assad has to go now faces a far more dangerous foe isis. But isis has a problem. Its almost out of western hostages. At least one american is still missing in the middle east, journalist austin tyke. But isis might not have him. They do have british journalist john cantlie and views him as a mouthpiece. In a video released this week, cantlie calls to a isis supporters in the west to launch attacks. With the dwindling number of hostages left to kill, such attacks may be a way for isis to goad the west deeper into battle. Having and killing hostages has been a central way for isis to lash out at nations attacking it. Now that it is running out of hostages, the fear is isis could look for other ways to do that, lester. Richard engel tonight, thank you. Tonight u. S. Officials are telling nbc news the u. S. Will announce shortly that it is temporarily closing the American Embassy in yemen because of the governments takeover by hardline shiite rebels linked to iran. As unrest grew there three weeks ago, most personnel were already moved out and all but Emergency Services were suspended. The rebel Group Announced a formal takeover of the capital on friday, but the pentagon insisted today that critical american counterterror operations will continue inside the country. Tonight the snow has finally stopped falling in boston, for now. But as much as the city wants to dig out and get moving again, tempers have reached a boiling point as most mass transit has come to a grinding halt and there is more snow on the way. Nbcs ron mott remains in snowbound beantown for us tonight. Ron, good evening. Reporter hey, lester, good evening. This should be the evening rush, this whole plaza should be full of people trying to get underground to get a train home. But today there were no trains. Thats got a lot of people pointing fingers at the transit chief, and today she fired back. In every nook and cranny snow. So much the governor is calling up 500 members of the National Guard and asking neighboring states for help. On snowpacked railways, snowzillas are roaring, jetpowered blowers trying to clear the tracks for the morning commute. All in an effort to stop a repeat of this. Passengers stranded forced to walk, trains crippled. I want to move. I just want to get out of here. Reporter today a demand for answers. Everybody is tired as heck. They are frustrated as heck. They are mad as heck. And they want all of this snow to go away. Reporter bostons embattled transit chief Beverly Scott redirected blame to the citys aging rail system. For anyone to have any belief that a system thats over a hundred years old to think its going to have the resilience to wind up rebounding and flying like an eagle, thats absolutely the epitome of and im not going to say foolish. Reporter the governor called the disruptions unacceptable. Were dealing with unprecedented circumstances here. Everybodys scrambling and working enormously hard to deal with all the issues this creates. Reporter the heavy snow piling up for weeks, now triggering building and roof collapses, an urgent plea for people to clear theirs. And with so many homebound, including school kids theyve been out of school more than theyve been in school the last few weeks. Reporter parents like this woman says stress is piling up like snow. The last two days, folks getting into Downtown Boston from the suburban communities, its been incredibly stressful on the city as a whole. Reporter and theres no end in sight. One suburban town now dumping its snow in the ocean. There are two more quickmoving systems that could drop more accumulating snow thursday night and sunday. And then this weekend across the northeast, the coldest temperatures so far this season. Reporter now, government offices and schools are set to reopen tomorrow. The t is even promising limited service. Of course, theres all this snow to deal with. The mayor is again asking employers to be flexible and let people work from home. We learned today its now eight babies who have measles in a day care outside chicago which we first reported on last week. This outbreak has spread to at least 122 people nationwide triggering another alert today from Health Officials on capitol hill. They hope parents who have been afraid to vaccinate their children can now be convinced to change their minds. Our report tonight from nbcs hallie jackson. Reporter the baileys in Southern California never planned on giving kingston the measles vaccine until now. What changed your mind . We had the Measles Outbreak happening in our backyard. These diseases that i think our generation is not too familiar with. I have to make sure that hes safe. Reporter eileen and her husband examples of a new attitude Health Officials hope to see more of to stop the spread of measles now reported in 18 states and d. C. This year. On capitol hill today, warnings this may grow because of clusters of people who choose not to immunize. Some of those unvaccinated microcommunities may be getting larger. Reporter changing those minds can be hard. A study in pediatrics found provaccine messages actually backfired with some parents already opposed to immunization make them feel defensive and less likely to vaccinate their kids down the road. Doctors say another group of people are at risk, too, parents who think its safer to delay giving the measles shot, like courtney stewart. They were babies and i would go in for the vaccine and i felt really nervous, and it made me feel really uncomfortable. Reporter shes one of the estimated 13 of people who do not follow cdc guidelines which recommend the first vaccine by 18 months. Levi is 5, and this is his first shot ever. Doing this today, i didnt hesitate. I didnt feel like there was going to be any problems with it. I dont feel bullied into it. How was it . Reporter doctors say parents should stick to the schedule since delaying the vaccine can make it less effective. A lot of my decisionmaking was based more on fear not facts. If i could go back in time, i really would have done my research. Reporter and public Health Officials hope that message is what spreads now. Hallie jackson, nbc news, irvine, california. Some terrifying moments aboard a u. S. Airways plane forced to make an Emergency Landing in houston. It happened overnight aboard a flight out of philadelphia. When it was time to land, the nose gear would not deploy. It wasnt pretty but the pilot managed to rest the plane down easily on that nose. 56 people were aboard, at least one was taken to the hospital with minor injuries. Now to Southern California on a wild chase through the streets and freeways of los angeles. An armed suspect on the run, police on his trail. A very dangerous situation playing out last night as he slammed into several drivers along the way and then carjacked a woman at gunpoint. All of it caught on camera. We get our report from nbcs miguel almaguer. Reporter rush hour in los angeles. A highspeed pursuit for a suspect in a stolen car weaving across freeways through red lights and often the wrong way. Its so dangerous. So, so dangerous. Reporter the drama televised live. Weve got Police Chasing a suspect down there. Reporter the intense chase lasts 45 minutes. Hitting vehicles left and right. Reporter four vehicles are rammed. Ditching his mangled car, now hes on foot. A 22yearold woman is carjacked. I see them running towards me. I just kind of froze. I tried to pull my son. I stopped the car and ran. Reporter after attempting a second carjacking, the suspect is shot and wounded. The suspect is down. Reporter incredibly, no other serious injuries. In a city known for wild pursuits, this is one of the most dramatic. Miguel almaguer, nbc news, los angeles. Big news from the world of business and technology. Listen to this. Tonight apple has become the First American company to close the day worth more than 700 billion. Thats roughly the equivalent of 100 for every man, woman and child on earth. Not that theyre planning on giving it away. Still ahead here tonight, Chronic Fatigue. A mysterious and often misunderstood disease. Doctors say its very real, and theyre laying out the specific symptoms you should be looking for. Also, paying it forward. A slice at a time, something really special happening with pizza. In this day and age, ask most americans if theyre tired, and the answer will probably be a big yes. Thats why people who suffer from Chronic Fatigue syndrome can have a hard time being taken seriously even by their doctors. But today a prominent medical panel declared that this syndrome is not only real, but the vast majority of people who suffer from it havent even been diagnosed. Our report on that tonight from nbcs anne thompson. You ready to get dressed . Reporter morning rush at this familys home. Robin and warren get themselves and their daughters ready for dont forget your penguin. Reporter but robin battles more than the clock. She has Chronic Fatigue syndrome. No matter how much i sleep, im still tired. Reporter it started when robin was just 23. After three years of doctors appointments and tests, she finally got a diagnosis. How hard was it to convince doctors something was wrong . It was very hard. So i remember being told that you just need to relax more. Reporter calling it a serious debilitating condition. Today the institute of medicine issued a new set of symptoms to help doctors recognize the disease. Patients must have a dropoff in normal activity for more than six months with profound exhaustion. Sleep that doesnt refresh. And symptoms that get worse after physical or mental exertion. Plus either cognitive impairment, what patients call brain fog, or symptoms that only improve when the patient lies down. It affects up to 2. 5 million americans more famously laura hillenbrand, author of seabiscuit and unbroken. It clearly defines this illness as a physical disease. And i use the word disease not a syndrome. Reporter thats reflected in the new name recommended by the institute, systemic exertion intolerance disease, a real disease with real consequences for its sufferers. Anne thompson nbc news, white plains, new york. Our medical contributor dr. Natalie azar joins us now. Shes a rheumatologist and treats Chronic Fatigue disease. Natalie, how hard has it been to diagnose and treat this . Incredibly hard, lester. Its what we call a clinical diagnosis which means there is no diagnostic test. We base it really on the patients history, physical exam, and excluding other disorders that can mimic it. Treatment varies. Some people are candidates for medicine, Cognitive Behavioral Therapy can be very effective. Exercise can be very effective. But i think whats highlighted in the segment here is its really brought this syndrome or disease to light, validation to parents and a very good education for physicians across a whole range of disciplines so they can better diagnosis and refer patients to physicians who can manage them. A real problem that people are suffering from. Exactly. Dr. Azar, thanks very much. Thank you. Were back in a moment with a big show caught on camera at a vegas casino after dark, where things didnt exactly go quite as planned. If youve ever had one of those days where it feels like the cosmos is smiling down upon you maybe you were more right than you know. The Hubble Telescope caught this image that looks an awful lot like a smiley face in space. In actuality, the two points of light that look like the eyes are separate distant galaxies, and the smile is an effect caused by gravitational warping. The biggest show in vegas last night didnt happen on any stage. Rather it was the implosion of 12story clarion casino hotel near the strip known for years as the debbie reynolds, who used to own it. Not everything happened as plan. The elevator core remained standing. Leaning to the side. Crews are now working to finish the job. Late word in a big change in late night tv. After years behind the desk job stewart told his audience tonight hell step down as host of the daily show later this year. They call stewart a comic genius, generous with his time and talent. No word on whats next for stewart. When we come back its sort of like a take a penny, leave the penny idea. If the pennies, that, added up to pizza. Nbc nightly news is brought to you by pacific life. For insurance, annuities and mutual funds, choose pacific life. The power to help you succeed. Any Office Manager looking to boost morale will tell you, so will any parent hosting a sleepover party, few things in this world enjenger as much goodwill as springing for pizza. At one pizza shop in philadelphia, customers can spread that goodwill every time they order a slice. Nbcs chanel jones has tonights making a difference report. Reporter walk into rosas fresh pizza, and youll see, its not your ordinary pizza shop. Lining these walls, thousands of postit notes, each worth one free slice, put there by a customer who wanted to help feed someone in need by donating a dollar slice. Thank you. Weve given away 9,000 slices so far. Reporter Mason Wartman left a career on wall street to run his own business. Its own pressure cooker. On bad days i wish i wouldnt do this, and on good days im like, im really glad i did this. At the end of the day, we help so many people that i cant go back. Reporter mason admits he didnt start out intending to feed the needy. It was his customers who cooked up the idea and now keep it going, feeding about 40 people every day. Ive been doing this. It feels great to be able to help somebody else. Reporter they leave a postit note with a message. Do you have a favorite . Yeah. I like this one right here. Its an Angel Holding a hot slice of pizza with a little heart inside. Reporter it doesnt feel so much like a handout to casey, homeless for six months. Its not something youre begging from someone else. The fact that it was a gift makes it taste just that much better. We recognize them just like paying customers. Just like any other restaurant recognizes their customers. Reporter for those in need, its food for the soul. Chanel jones, nbc news, philadelphia. Thats our broadcast for this tuesday night. Thank you for being with us. Im lester holt in for brian. We hope you to see you right back here tomorrow evening. Good night. Its not just in the schools. Its everywhere. Its in the libraries. Its in the airplanes. Its in the grocery stores. Right now at 6 00 a fathers push to fight potentially dangerous viruses in schools is being heard tonight. Good evening, everybody. The measles debate is getting heated at a School Board Meeting tonight drawing national attention. The father of a first grader wants to ban students who have not been vaccinated. Nbc bay areas Mark Matthews is in tiburon this evening. Political power players are also there tonight. Reporter we have a couple state senators one state senator and a representative from another and a state assemblyman here. The meeting just getting under way. We first told you about the parents pressing a case with the school here in tiburon. Tonight they are asking these state lawmakers to repeal the exemption that allows parents to opt out of vaccinations. This 6yearold boy cannot be vaccinated because his system is not strong enough. Hes been battling leukemia. Not only would they be at higher risk for more severe forms of illness from measles for example, but likely it would delay their therapy. Were hoping theres some person or