on our broadcast tonight, bracing for battle. claims of mass executions now in iraq, and a tense scene in baghdad tonight. marines arriving to evacuate americans and richard engel is there as the u.s. moves warships into the gulf. tornado outbreak. twisters on the ground. this evening, the unbelievable power caught on camera as multiple funnels touched down at once. facebook threats. when does what people write on the web cross the line and become a crime? that's the big question tonight, and the outcome affects everyone who posts anything. and risk factors as american kids consume more caffeine than ever. tonight, a startling look at how even a little is affecting their health and hitting boys differently than girls. "nightly news" begins now.

good evening. as a group of heavily armed and highly motivated terrorists continues its way across iraq, it's not yet clear if the u.s. will take any action in iraq. the president has ruled out any troops, and the american people aren't at all sure we should take any action even though what's happening now is a direct outgrowth of the u.s. invasion there over a decade ago. the u.s. has started removing some of its staff from the fortress-like u.s. embassy in baghdad, calling this a relocation and not an evacuation. u.s. marine helicopters will come and go from a navy vessel in the persian gulf where the u.s. has sent an aircraft carrier and three destroyers. the u.s. may have to work with iran before this is all over as another iraqi city has now fallen to this group called isis. our chief foreign correspondent, richard engel, is back in baghdad tonight to start our coverage off. richard, start with what it's

like there right now. >> reporter: good evening, brian. there is a curfew in place here, and there is absolutely no one on the street. that is, no civilians. there are lots and lots of police officers out, checkpoints every few hundred yards. parts of iraq fell quickly to that militant group, not baghdad. here, they are bracing for a fight. these iraqi soldiers, prisoners of isis, in a video not verified by nbc news, are being forced to swear allegiance to the al qaeda offshoot that overran their position. one refuses and is executed. the others agreed, but they, too, were later found dead. they are getting stronger, joined by supporters of saddam hussein and sunni tribal leaders. in mosul they march together on their way to hang an iraqi soldier. this weekend, the militants released pictures of dozens of iraqi soldiers being led to

their death. the iraqi army is now fighting back with air strikes and thousands of new recruits. but the insurgents have their sights on baghdad, and if they can't get to it, they may try to send in suicide bombers instead. it is strange to come back to baghdad and see it like this. this is normally the busiest market in the city. today all of the shops are closed, and this street is normally full of traffic. today, hardly anything. and there are gunmen on every corner. some are soldiers. many are shiite militiamen responding to a call to arms from their religious leaders. they're ready to defend the capital and the shiite faith. we did find one shop open. a grocery owned by jamel karesh, he thinks the isis radicals aren't strong enough to enter baghdad now. instead, he expects car bombs. "people are afraid," he said. "we expect bombings will come at

any moment." this is perhaps the most iconic place in baghdad, the square. there used to be a giant statue of saddam hussein right on top of that pedestal until as we all saw, u.s. marines came down the street, the statue came down, and saddam's regime collapsed. iraq was at a turning point now, and it may be at a turning point now. as evening came, even fewer people were out in the city of seven million. bracing for a new round of sectarian war, perhaps the worst this country has ever seen. what's next, brian, could be a very difficult phase for this country. the iraqi government will try and retake some of the cities that have been captured by isis. that means the shiite government dropping bombs on civilian areas, on sunni cities. there will likely be a response with car bombings here in baghdad, and this could be a long fight. brian? >> richard engel back in baghdad

for us after many years of living there while covering the war. richard, thanks. and on the diplomacy front, it appears the u.s. is considering at least working with iran. at least the two countries are prepared to talk about working together to quell the violence in iraq. andrea mitchell monitoring all of it from our d.c. newsroom tonight. andrea, good evening. >> reporter: good evening, brian. with the militants now closing in on baghdad, tonight the president has notified congress he is sending up to 275 military personnel to iraq to help secure the embassy in baghdad. in addition, he has summoned his national security team to a crisis meeting at the white house tonight to weigh military options including possible air strikes that would include the insertion of ground forces to help determine the targets. also, among the topics of today's meeting, today's first talks between the u.s. and iran about iraq. in a classic case of strange bedfellows, the u.s. navy spoke to iran to save baghdad from falling. even as the leader of the national guard, the qods force, is in baghdad helping militias defend the capital.

>> we're open to discussions if there's something constructive that can be contributed by iran. if iran is prepared to do something that is going to respect the integrity and sovereignty of iraq and the ability of the government to reform. >> reporter: the talks between kerry's deputy, william burnes, and iran 's foreign ministers restarted today in vienna. the goal is to press iraq's prime minister maliki to include rival sunnis in his government, a key step toward a political solution. still, any talk of military cooperation with iran makes u.s. allies in the region, israel, and saudi arabia very nervous about any dealings with their adversary, iran. and among the military options are the limited use of special forces inside iraq if needed to help guide possible air strikes. brian? >> of course it could still be early yet in this crisis. andrea mitchell in our d.c. newsroom tonight. andrea, thanks.

in this country tonight, the army has officially opened its investigation into the disappearance of bowe bergdahl in afghanistan back in '09 and how he ended up in the hands of the taliban. they put a two-star army general in charge of the investigation, which we're told will not include an interview with bergdahl himself, not yet anyway, because they say it's too early in his recovery and that he is not yet up to it. tonight, weather forecasters have issued a statement about what they are calling a "particularly dangerous situation" as multiple tornadoes touch down in the middle of our country. the upper plains including one incredible scene tonight as two funnels touched down side by side at the same time. there are late reports of damage and possible injuries here. our own tom costello has details. >> reporter: near the nebraska/south dakota state line, a massive tornado dropped out of the sky late afternoon taking aim at the small farming town surrounding stanton. >> it's a really incredibly strong tornado with another secondary tornado, like i said,

wrapping around it. >> reporter: veteran storm chasers described at least two tornadoes dropping out of a pitch-black super cell, bringing with it hail two inches in diameter. multiple funnels, one of them a mile wide, chewing up farmland and throwing it hundreds of feet into the air. >> take cover now if you live there. >> reporter: the weather channel's radar showed a massive cell of red and orange. >> at one point, we saw three tornadoes on the ground, and looks like the town got the worst of it. the town of pilger, nebraska. >> reporter: interstate 275 in nebraska running through the heart of the zone. >> there's no reason to suspect that this particular storm is going to weaken any time soon. >> reporter: a violent afternoon in northeastern nebraska with concern it could be a very long night in the heartland. tom costello, nbc news, washington. while we just heard from him in tom's piece, we want to get more on this night ahead. we want to bring back in weather channel meteorologist and severe weather specialist dr. greg postel watching from weather channel headquarters tonight.

greg, what's doing this, and what's this a part of? >> we have a powerful storm system, brian, moving across the heartland of america. very strong jet stream. a lot of instability. big thunderstorms. as you saw, big time storm producers. this is from the pilger area in nebraska. you can see very strong destruction across the region. i'm afraid we may see more this evening into tonight. we are seeing tornado warnings also now across parts of iowa. you can see tornado warnings there. little boxes in red. each of those is a tornado warning. the whole complex of storm wills continue to roll eastward for several hours. kwo see it dying any time soon. we have tornado watches outlined in red across the region through much of the night. it will be a long night for tornadoes and long winds. brian back to you. >> greg, thanks, as always. on the west coast, a

wildfire burning out of control in california. thousands of acres have been charred so far. firefighters are now trying to protect hundreds of homes from the flames. nbc's miguel almaguer is in kernville, california, not far from bakersfield. miguel, good evening. >> reporter: brian, good evening. the so-called shirley fire is the most dangerous wildfire burning in california tonight. this is the reason why -- the whipping winds. some 2,000 acres have been charred so far, 1,000 homes are threatened at this very hour as the fire works its way through rural mountain areas after breaking out friday. the blaze more than doubled in size overnight, the air attack here is crucial. the fleet of helicopters and planes have slowed the fire's progress even as wind gusts have topped 30 miles per hour today. crews aren't taking any chances as they work ahead of this blaze. $4.2 million has been spent on fire suppression so far. a staggering number after just three days with many vacation homes, power lines, and communication facilities under threat.

some 1,100 firefighters are on the front lines. this blaze is roughly 10% contained. crews say they are making progress, but firefighters note these are conditions we typically see late in the fire season. as you know, this fire season is just getting underway. brian? >> miguel almaguer covering the hot fire outside of bakers field, california, in kernville. miguel, thanks. general motors announced another recall. this time almost 3.2 million vehicles for a grand total this year of 20 million worldwide. that is roughly equal to the total number of cars gm sold in the u.s. over the past seven years. it's all related to the key problem that has shut down cars' ignitions, power steering, brakes, air bags. we have put a full list of this new group of vehicles involved in this recall on our website tonight. that's nbcnews.com. u.s. supreme court agreed today to decide an increasingly common question in our digital

age in which people sometimes write things online that they might not say to your face. this particular case involves messages that someone posted on facebook. and the question before the justices is when does a threat written on the web cross the line from free speech to a crime? we get our report from our justice correspondent, pete williams. >> reporter: with more than 165 million americans now using social media, the experts call it digital courage. posting comments that probably wouldn't be said to someone's face. a worker at a pennsylvania amusement park, anthony alonis, got in big trouble four years ago after his wife left him and took their two children, leaving him despon department. ripping on a comedy troupe's routine about free speech -- >> it's illegal, a federal offense -- >> reporter: he wrote on his facebook page, "did you know it's illegal for me to say i want to kill my wife?" after she got a restraining order against him, he wrote, "put it in your pocket, is it

thick enough to stop a bullet?" two years before the shoot ing at sandy hook he wrote, "enough elementary schools in a ten-mile radius to initiate the most heinous school shooting imagined." he was found guilty of posting an online threat. the judge said it wasn't whether he intended to make a threat but whether a reasonable person would have considered the words threatening. a lawyer for him says the legal test doesn't work on the internet where it may not be obvious someone is just blowing off steam. >> these interactions are taking place online where people you've never met before can read your comments. and you know, they have no idea whether you meant it or not. >> reporter: the obama administration says the law is intended to protect people from the fear of a violent attack. but legal experts say the test needs updating. >> it's important in terms of what constitutes a true threat because the person who feels threatened may have been someone who was not intended to ever see or hear this communication. >> reporter: now the justices will decide whether the medium counts as much as the message.

pete williams, nbc news at the supreme court. still ahead for us on a monday night, what we've learned about kids and caffeine. how much they're consuming and what even a little bit is doing to their bodies. then later, he's off. a future king with big shoes to fill makes a big move with everybody watching.

of course there's a first for every new american generation, and no matter what this current generation later achieves, they will be known for, among other thing, their consumption of caffeine. they are consuming it like never before. 75% of them in something they eat or drink. and tonight in health news, there's a warning about what even a small amount of caffeine can do to children, especially boys. we get the story tonight from our chief medical editor, dr. nancy snyderman. >> reporter: tara and mitch lieberman say their boys have so much energy -- >> here's water -- >> reporter: they carefully limit the amount of caffeine their kids consume.

>> i just feel that it's healthier to give them juices with low sugar amounts, water, milk. stuff like that. >> reporter: caffeine is hard to avoid these days. no longer just in coffee, tea, and colas, it's now added to many new products from energy drinks to snacks and candy. and while we've known for some time that caffeine raises blood pressure and lowers heart rate, today's study in the journal "pediatrics" reveals how it affects boys and girls differently after puberty. the report from the university of buffalo studied the impact of even small amounts of caffeine on children ages 8 to 9 and on teenagers ages 15 to 17. the younger kids got approximately the caffeine equivalent of a half to full can of soda. the teens got one to two cans

worth. among all groups, the teenaged boys experienced slightly higher blood pressure levels than the girls. researchers in this study aren't sure why teenage boys are more sensitive to caffeine but suspect it may have to do with hormones. and another concern -- the effect of caffeine on millions of kids with other medical issues like adhd. >> if you take asthma medication, if you take other medications, behavioral medications, this can be a big problem. it is something that has a biological effect on our bodies, and you have to be careful. >> reporter: last year the food and drug administration suggested that we start to look at the safety of added caffeine to products. but the problem is, bottom line, no younger children should have it, and teenagers should not be fooled by the promise of an energy boost. caffeine is a stimulant. real energy comes the old-fashioned way -- by eating well and getting enough sleep. brian? >> dr. nancy snyderman, thank you as always. another break. we're back in a moment with the news tonight about a place that changed the course of modern american history.

saturday -- sadness in the baseball world with the death of tony gwynn. he was a hitter, one of the best ever, with over 3,100 lifetime, a career average of .338. that career was devoted to san diego and the padres. all 20 years of it, including 15 trips to the all-star game and membership in the hall of fame. tony gwynn, mr. padre, died today at just the age of 54. he succumbed to cancer of the mouth and salivary glands which he attributed to years of chewing tobacco. it was a sad weekend in the nfl, especially in the city of pittsburgh, after the news of the death of chuck knoll. he stook over the steelers and turned them around. he invented the steel curtain defense and spectacular offense. his steelers won the super bowl in '74, '75, '78, '79, he drafted, bradshaw, harris, green, swann, webster, and lambert. he played for the legendary paul brown before becoming a legend himself.

chuck knoll was 82 years old. tomorrow marks 42 years since the watergate break-in. watergate's been back in the news of late because of a structure that played a big role in the story. the parking garage in rosalyn, virginia, where bob woodward met his source, deep throat, who we now know was mark felt. that garage is coming down to make way for a commercial and residential complex. there is a marker out at the curb telling people the significance of the site. and the news from the u.k. this past weekend was this -- the future king of england can now walk. prince george, third in line to the throne, showed a combo of walking and crawling skills as his mother, the duchess, watched, and his dad played in a charity polo match. when we come back, remembering the voice of a generation.

finally tonight, back to a time when radio was everything portable, ubiquitous, and playing the soundtrack of our lives. and spinning that soundtrack was casey kasem. while he was in the news most recently because of troubles in his family, during his own struggle with a form of dementia, his death this past weekend reminded us of a time when it seemed downright possible to reach for the stars.

we get a look back tonight from nbc's rehema ellis. >> reporter: long before fans recognized his face, they knew that voice. >> i'm casey kasem, and the countdown continues. ♪ number 37 >> reporter: for nearly four decades, he defined sunday morning radio. before music was digitized and downloaded on demand, kasem brought generations of music lovers together, playing "america's top 40" songs from coast to coast. >> hot off the record charts of "billboard magazine" for the week ending july 11th, 1970 -- >> reporter: kasem never imagined this life. >> my first priority is not music. when i'm at home, i don't listen to music. >> reporter: a lebanese american, born in detroit in 1932, he dreamed of becoming a baseball player but found his voice as a deejay with armed forces radio during the korean war. in 1970, he launched "american top 40" on radio and later a version on tv.

>> now we're up to the number-one song in the usa -- >> reporter: in 2004, he handed the microphone to ryan seacrest. >> i remember saying to him, "look, i'm nervous and a little scared because -- you are the guy that has done this for so long." he just said, "just count backwards, and have fun. you'll be great." >> reporter: his style was positive, upbeat, and often emotional. >> dear casey -- >> reporter: his signature long distance dedication made his shows personal. >> maybe my desiree in germany will hear it and know it's for her. >> reporter: he made a fortune in voiceovers as shaggy in the "scooby doo" series -- >> maybe you didn't pay the electric bill -- >> reporter: commercials -- >> come on in hungry. >> reporter: even as the voice of nbc. >> this is nbc. >> reporter: his famous tag line was the rule he said he tried to live by -- >> keep your feet on the ground, but keep reaching for the stars. >> reporter: casey kasem's iconic voice now part of american history. rehema ellis, nbc news, new york. that's our broadcast on a monday night as we start off a

new week. thank you for being here with us. i'm brian williams, and we hope to see you right back here tomorrow evening. to see you right back here tomorrow evening. good night. -- captions by vitac -- www.vitac.com nbc bay area news starts now. right now at 6:00, it's called audrie's law. some say it would doom the juvenile justice system. >> outrage tonight from the parents of the girl on the eve of a critical vote. they will decide whether the law can move forward. it's named after the girl who committed suicide after being sexually assaulted at a party.

it would expand the definition of rape. but opponents are pushing back saying she was never actually sexually assaulted. i know you spoke to the family. >> reporter: i certainly did, jessica. opponents of this bill say it is not justice. they are calling it vengeance. and they say it would -- at a house party, they say she was sexually assaulted and photographed. photos circulated and ultimately, audrie took her own life. now nearly two years, the safety committee will make a decision on whether a proposed cyber bullying law named for the teen should move forward. her attackers received punishments of just 30 to 45 days. the center on juvenile justice