on the broadcast tonight, tragic confirmation. worst fears realized for the family of the last american held by isis. her powerful final message in a letter smuggled to her family. tonight, the mystery of how and when she died. out of control, tempers flare as over six feet of snow pile up on roads and roofs. there's nowhere to put it and there's more snow on the way. caught on camera, a wild chase through southern california, an armed suspect on the run, crashing, carjacking, and a woman's split-second decision at the point of a gun. and chronic fatigue syndrome, misunderstood and often underdiagnosed especially among women. doctors say it's very real, and they're laying out the symptoms to look for. "nightly news" begins now.

>> announcer: from nbc news world headquarters in new york, this is "nbc nightly news" with brian williams. >> good evening, i'm lester holt sitting in tonight for brian. anxious months and months of hope and worry has turned to unimaginable grief today for family and friends of 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 fryer reports from her hometown, prescott, arizona. >> reporter: emotions are strong tonight in kayla mueller's

hometown a year and a half after she was taken captive by isis. 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 it's difficult to determine the cause of death. in a statement mueller's 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. i'm not breaking down and i will not give in, no matter how long it takes. >> i am in solidarity with the syrian people. >> reporter: 26-year-old mueller was working for aid groups along

the turkish/syrian border in august 2013 when she was captured near aleppo. 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 kayla's 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 mueller's return. tonight, they're grieving her loss. >> she was a fine young lady. that's for sure. and she's done prescott well. >> reporter: in mueller's letter which was smuggled out by her cell mate, she said at the time she was in a safe location, completely unharmed and healthy eated with respect. what's unclear tonight is how exactly she died and when. >> joe fryer, thanks. kayla mueller's death follows months of shear horror,

journalists and aid workers beheaded, a jordanian military pilot burned alive. 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 there's a good deal of force being applied already. our chief attorney correspondent richard 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 jordan's air force in an interview with nbc's kiera simmons. isis also claims the u.s. is allied with syrian president assad, because they're both bombing isis. in a rare interview, assad hinted to the bbc that the two countries are in touch, though not directly. >> there's no 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 had to go. now faces a far more dangerous foe, isis. but isis has a problem. it's almost out of western hostages. at least one american is still missing in the middle east,

austin tyke. they do have british journalist john can't -- cantly and use him as a mouthpiece. in a video released this week, he calls on 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 go 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 government's takeover by hard line 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. tempers have reached a boiling point as most mass transit has come to a grinding halt and there is more snow on the way. nbc's ron motte remains in snow-bound 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. today there were no trains. that's 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 snow-packed railways, snowzillas are roaring, trying to clear the tracks for a morning commute.

all in an effort to stop a repeat of this. passengers 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: boston's embattled transit chief beverly scott redirected blame to the aging rail system. >> for anyone to have any belief that a system that's over 100 years old, to think it's going to have the resilience to wind up rebounding and flying like an eagle, that is absolutely the epitome of, and i'm not going to say foolish. >> reporter: the governor called the disruptions unacceptable. >> we're dealing with unprecedented circumstances here. everybody's 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, and urgent plea for people to clear theirs. and with so many homebound,

including school kids -- >> they've been out of school more than they've been in school the last few weeks. >> reporter: parents say stress is piling up like the snow. >> the last two days, folks getting into downtown boston from the suburban communities, it's been incredibly stressful on the city as a whole. >> reporter: and there's no end in sight. one suburban town now dumping its snow in the ocean. >> there are two more quick-moving systems that could drop 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 promising limited service. of course there's all this snow to deal with. the mayor is asking to be flexible and let people work from home another day. we learned today it's 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 nbc's halle 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 he's safe. >> reporter: eileen and her husband examples of a new attitude that health officials hope to see more of, to stop the spread of measles, 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 pro-vaccine messages actually backfired with some parents already opposed to immunization, making 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 it's safer to delay giving the measles shot, like courtney stewart. >> they were babies and i would vaccine and i felt really nervous, and it made me feel really uncomfortable. >> reporter: she's the estimated 13% of people who do not follow the cdc guidelines which recommend vaccines by 18 months. levi is 5, and this is his first shotter. >> doing this today, i didn't hesitate. i felt so bullied into it. >> reporter: doctors say parents should stick to the schedule since delaying the vaccine can make it less effective. >> a lot of my decision-making 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. halle jackson, nbc news, irvine, california. 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 wasn't 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. to southern california, 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 gun point. all of it caught on camera. we get our report from nbc's miguel almaguer tonight. >> reporter: rush hour in los angeles. a high-speed pursuit for a suspect in a stolen car, weaving across freeways, through red lights and often the wrong way. >> it's so dangerous. >> reporter: the drama televised live. >> we've got police chasing a suspect down there. >> reporter: the intense chase lasts 45 minutes. four vehicles are rammed.

ditching his mangled car, now he's on foot. a 22-year-old woman is carjacked. >> i see them running towards me, i kind of froze. i stopped the car. >> reporter: after attempting a second carjacking, the suspect is shot and wounded. 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 in technology. listen to this. tonight apple has become the first american company to close the day worth more than $700 billion. that's roughly the equivalent of $100 for every man, woman and child on earth. not that they're planning on giving it away. still ahead here tonight, chronic fatigue, a mysterious

and often misunderstood disease. doctors say it's very real, and they're 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. but when i started having back pain my sister had to come help. i don't like asking for help. i took tylenol but i had to take six pills to get through the day. so my daughter brought over some aleve. it's just two pills, all day! and now, i'm back! aleve. two pills. all day strong, all day long. and now introducing aleve pm for a better am. at ally bank no branches equals great rates. it's a fact. kind of like mute buttons equal danger. ...that sound good? not being on this phone call sounds good. it's not muted. was that you jason? it was geoffrey! it was jason. it could've been brenda.

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in this day and age, ask most americans if they're tired, and the answer will probably be a big yes. that's 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 haven't even been diagnosed. our report on that tonight from nbc's ann thompson. >> reporter: morning rush at this family's home. robin and warren get themselves and their daughters ready for the day. but robin battles more than the clock. she has chronic fatigue syndrome. >> no matter how much i sleep, i'm 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. 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 drop-off in normal activity for more than six months with profound

exhaustion sleep that doesn't refresh, and symptoms that get worse after physical or mental exertion, plus either cognitive impairment, what patients call brain fog, or symptoms only improves when the patient lies down. it affects up to 2.5 million americans, more famously, the 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: that's reflected in the new name recommended by the institute, systemic exertion intolerance disease, a real disease with real consequences for its sufferers. ann thompson, nbc news, white plains, new york. >> our medical contributor joins us, a rheumatologist and treats chronic fatigue disease. natalie, how hard has it been to diagnose and treat this? >> incredibly hard lester.

there is no diagnostic test. we base it really on the patient's history, physical exam, and excluding other disorders that can mimic it. treatment varies. some people are candidates for medicine, cognitive behaveioral therapy can be effective, exercise can be very effective. what's highlighted in the segment here is it's brought this disease or syndrome to light. it's a very good education for physicians across a whole range of disciplines so they can better diagnose and refer patients to physicians who can manage them. >> a real problem that people are suffering from. >> exactly. >> thanks very much. >> thank you. we're back in a moment with a big show caught on camera at a vegas casino after dark, where things didn't exactly go quite as planned. toenail fungus? don't hide it... tackle it with new fda-approved jublia! jublia is a prescription medicine proven to treat toenail fungus. use jublia as instructed by your doctor.

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with 3 types of good bacteria. live the regular life. phillips' the world is filled with air. but for people with copd sometimes breathing air can be difficult. if you have copd, ask your doctor about once-daily anoro ellipta. it helps people with copd breathe better for a full 24hours. anoro ellipta is the first fda-approved product containing two long-acting bronchodilators in one inhaler. anoro is not for asthma. anoro contains a type of medicine that increases risk of death in people with asthma. it is not known if this risk is increased in copd. anoro won't replace rescue inhalers for sudden copd symptoms and should not be used more than once a day. tell your doctor if you have a heart condition, or high blood pressure. tell your doctor if you have glaucoma, prostate or bladder problems, or problems passing urine as anoro may make these problems worse. call your doctor right away if you have worsened breathing chest pain, swelling of your mouth or tongue,

problems urinating or eye problems including vision changes or eye pain while taking anoro. nothing can reverse copd. the world is filled with air and anoro is helping people with copd breath air better. get your first prescription free at anoro.com. if you've ever had one of those days where it feels like the cosmos are 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 didn't happen on any stage, instead it was the implosion of the clarion casino hotel near the strip known for years as the debbie reynolds, who owned it. not everything happened as plan. the elevator core remained standing. leaning to the side. crews are now working to finish the job. when we come back, it's sort of like a take a penny leave a penny idea, if the penny, that is, is a pizza. penny, that is, is a pizza. ♪ during its first year,

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nobody told us to expect it... intercourse that's painful due to menopausal changes it's not likely to go away on its own. so let's do something about it. premarin vaginal cream can help it provides estrogens to help rebuild vaginal tissue and make intercourse more comfortable. premarin vaginal cream treats vaginal changes due to menopause and moderate-to-severe painful intercourse caused by these changes. don't use it if you've had unusual bleeding breast or uterine cancer blood clots, liver problems, stroke or heart attack, are allergic to any of its

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philadelphia customers can spread that goodwill every time they order a slice. nbc's chanel jones has tonight's making a difference report. >> reporter: walk into rosa's fresh pizza, and you'll see, it's not your ordinary pizza shop. lining these walls, thousands of post-it notes, each worth one free slice, put there by a customer who wanted to feed someone in need, by donating a dollar slice. >> we've given away 9,000 slices so far. >> reporter: mason left a three-year career on wall street to run his own business. its own pressure cooker. >> on bad days i wish i wouldn't do this, and on good days i'm like, i'm really glad i did this. at the end of the day, we help so many people, that i can't go back. >> reporter: mason admits he didn't 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. >> i've been doing this. it feels great to be able to help somebody else. >> reporter: they leave a post-it note with a message.

do you have a favorite? >> yeah. i like this one right here. it's an angel holding a hot slice of pizza with a heart inside. >> reporter: it doesn't feel so much like a handout to casey, homeless for six months. >> it's not something you're begging from someone else. the fact that it's a gift makes it taste that much better. >> we recognize them just like any paying customer. just like any other restaurant recognizes their customers. >> reporter: for those in need, it's food for the soul. chanel jones, nbc news, philadelphia. that's our broadcast for this tuesday night. thank you for being with us. i'm lester holt in for brian. we hope you to see you right back here tomorrow evening. good night. [screams] oh! [howls] (adam) you're going down, son. [laughs]

lights, camera, access. anybody who is enjoying a destruction of this man -- >> a powerful thing called trust. >> that disturbs me. >> you really really distrust him though? >> fire or forgive? i'm billy bush. we've got new