but it is soviet-built, aging rapidly. one reason he's accelerating his push for nuclear weapons. >> we are all united in the fact that north korea will not be accepted as a nuclear power. >> reporter: pyongyang has had nuclear weapons for at least a decade and may now have one small enough to be delivered on a missile. an alarming assessment by the defense intelligence agency or d.i.a. blurted out thursday by a congressman on the armed services committee. >> general, would you agree with that assessment by d.i.a.? >> i can't touch that one. because i'm not sure now -- it hasn't been released. >> reporter: the d.i.a. report was supposed to be kept classified but someone at the spy agency forgot to label it properly. today kerry and other u.s. officials insisted there is no proof north korea has the ability to put a nuclear warhead on a missile that could be successfully launched, reenter the atmosphere, and hit a target.

>> obviously, they have conducted a nuclear test. so there is some kind of device, but that is very different from miniaturization and delivery. >> reporter: who can get through to north korea? its closest ally is china where kerry is headed next amid signs that beijing may be growing weary of its increasingly reckless neighbor. >> they've got to try to defuse the situation. they can do that, it seems to me, by exercising more pressure on the economic relief that they provide the north koreans. >> reporter: but so far china has only stepped up its criticism of kim, not using its real power to stop him from carrying out threats. as secretary kerry heads to beijing he wants to see real action from china, not more words. brian? >> andrea mitchell starting off our coverage from seoul tonight. thanks. as the drama continues to play out on the world stage, the motives behind the actions of north korea starting to be a little bit more clear. something of a trade-off the north perhaps expects to get out of this. we get that part of the story

tonight from our chief foreign correspondent richard engel. >> reporter: analysts say north korea doesn't want nuclear war. that would be suicidal. along the border there are no signs it's mobilizing for one. ultimately, this is about money. using threats as blackmail for aid and to advertise north korea's weapons to sell them to other rogue states. >> about raising the profile of the new leader, presenting him as a hero. it's also about squeezing more money from the outside world. >> reporter: so far the strategy is working. north korea has captured the world's attention, gotten the u.s. to react. it is no accident. several of the most outlandish threats issued in the middle of the night in korea have been perfectly timed for american television. north korea has become a sensation online. a country that severely limits internet access for its own

people is trending worldwide on twitter. searched on google more than ever before. what's the attraction? strange propaganda. the leader coming off like a movie villain. chubby, odd haircut, carrying a gun, poring over attack plans for america's destruction with troops that slavishly follow him, doing anything to catch a glimpse of their infallible leader. crazy like a fox. >> first they manufacture a crisis and then they essentially extract payment to back off. >> reporter: analysts expect north korea will launch its missile and then ask for money not to do it again. until it needs more money the next time. brian, we are all still waiting for that missile test. perhaps monday. that's when festivities in pyongyang culminate, but the test won't end it. the question now is how to deal with a rogue state using nuclear

weapons for blackmail. brian? >> richard engel part of our team in seoul tonight. richard, thanks. now to this country and the big storm system that brought extreme weather to most of the country this week on its way east. it continues to move to the east coast tonight with snow and ice storms still trailing it across parts of the midwest. in the south, violent thunderstorms and tornadoes have left a lot of destruction behind. nbc's gabe gutierrez has the report from mississippi tonight. >> holy -- >> reporter: an up-close look at a violent twister near prairie point, mississippi. >> look at the house. holy mackerel. >> reporter: the man who shot the video says he watched his friend's house disappear. fortunately no one was home. >> the folks that are here that have lost everything that they have, it can't get much worse for them. >> reporter: the storms that killed one person and injured five in mississippi thursday were part of a massive system that stretched from canada to the gulf of mexico. >> we have been tracking the

storm complex for four days across the plains and the southeast. the tornadoes that touched down here in mississippi, they have done significant damage and the wind speeds would have to be at least 120 miles per hour to do this kind of damage. >> reporter: irvin hill was sleeping in his mobile home when a tornado lifted and tossed the structure. >> everything went up together. it went up in the sky. next thing i knew i landed out there up under that tree. >> reporter: heavy storms claimed two more lives in nebraska and missouri before they dumped hail and ripped off roofs near atlanta. today in huntsville, alabama, the hum of chainsaws as the national weather service confirmed two tornadoes there. >> i sent pictures to my children. i raised my kids here. it's hard. yeah. >> reporter: and that's why people like irvin hill say they will rebuild. >> i survived.

that's the amazing part. >> reporter: a second chance after being caught inside the storm. the national weather service just confirmed that this tornado was an ef-3 with winds of up to 165 miles per hour, brian. >> gabe gutierrez in mississippi tonight for us. gabe, thanks. law enforcement officials in arizona today said a package sent to the high profile and controversial sheriff joe arpaio would have exploded and caused serious injury or killed someone if it had been open, but an alert mail carrier noticed something wrong and flagged it for inspection. arpaio is fond of calling himself the toughest sheriff in america. told reporters today he's concerned for his family's safety and added, i didn't ask for all these threats. several law enforcement officials have been murdered in recent days including colorado's director of prisons and a texas district attorney. on tonight's broadcast of "rock center" we hear from the wife of the late apple visionary steve jobs, laurene powell jobs.

she goes before cameras rarely. she prefers to operate quietly as a philanthropist but has chosen to do so tonight because of a cause -- immigration, and the dream act. with recent polling showing 64% of americans now favor allowing undocumented immigrants to have the opportunity to become legal citizens, this is the cause that brought her east from california this past week. she is one of the least likely people to take a public stand or join in a demonstration on capitol hill. laurene powell jobs, wife of the late steve jobs is an intensely private person. but with the film maker, davis guggenheim, she went to washington this week to push for immigration reform, especially on behalf of young undocumented immigrants. guggenheim is the man behind oscar winning film "an

inconvenient truth" and "waiting for superman." he and powell jobs screened the film for congress. it is called "the dream is now." >> i'm undocumented. >> i'm undocumented. >> i'm undocumented, unafraid and unashamed. >> there is movement on both sides. there is enough acknowledgment that this is a time when we can get serious legislation passed. so that's why we are willing to raise our voices to pledge so much time and passion and energy towards helping in any way we can to get this done. >> do you care how they come to it? do you care how they get there? do you care if rand paul chooses to say these are potential taxpayers? do you care if some people say, look, if it keeps my kid out of the marine corps, that's fine? do you care how they come to it as long as the vote goes your way? >> i think people are motivated in different ways. i don't mind if someone comes at immigration reform to expand the tax base. because i know individuals who

are caught in this purgatory, all i want to do is help find some redress so that they can live fully productive lives. if it means that we have strange bedfellows, so be it. >> one more thing here. laurene powell jobs made it very clear for reasons of family and privacy she did not want to discuss her husband's death. she says she never will. she was willing to talk with us about what he left to us all. >> his private legacy with me and the kids is that of husband and father. we miss him every day. having the body of work surrounding us is actually really a beautiful reminder. >> we will air our conversation with laurene powell jobs on an all new "rock center" tonight at 10:00 p.m./9:00 central. president and mrs. obama

released their tax returns today. their income was down from the year before mostly because income was down from the sale of his books. still, the obamas' adjusted gross income for 2012 just over $608,000. they paid about $112,000 in total tax. works out to a tax rate of 18.4%. the white house was quick to note today the president thinks his tax rate is too low. still ahead for us tonight, the growing number of older americans on the cutting edge. getting up to speed and fast for a very good and basic reason. later, the comic legend being remembered tonight as one of the all-time greats.

>> announcer: the road to retirement, brought to you by fidelity investments. take control of your personal economy. >> after several years of not that much technological growth,

america's seniors are turning to computer use more than ever before. the folks at the pugh research center now say the gains are significant. one of the reasons behind the sharp increase may be this stat from the aarp which estimates roughly half of all grandparents in this country live at least 400 miles away from the grandkids. as our own chris jansing reports tonight, they are prompted by the very simple motive of keeping in touch. >> do you hear clicking? >> no! >> reporter: the trials and tribulations of tech challenged seniors have become the stuff of youtube sensation. >> why won't it take a picture? [ speaking in a foreign language ] >> reporter: and fodder for funny commercials. but an ipad is an awfully expensive cutting board. >> images.google. >> reporter: seniors are flocking to classes to get up to social media speed. >> my social friends push me because they want me to "tweeter" and "twit." >> it's a nice day to update your family. >> reporter: in california this session is focused on connecting with friends and family through facebook.

>> they send me things. i think i have responded and i haven't. i don't get any responses back. >> click on it and drag it. >> reporter: slowly but surely, seniors are embracing social media. for the first time ever last year more than half of seniors were online. a third now use social media websites. >> wow. i really love that. >> reporter: interactive video programs like skype and facetime are building a base of silver surfers like barbara zack in florida who uses it to connect to far away family. >> i can watch my grandchildren grow up. i can watch them in their daily lives. that, to me, is priceless. >> reporter: in ohio, nancy lemon learned to text when her teenage grandson stopped answering his phone. >> when i get a message from him saying "i love you" it makes it all worth it. >> reporter: there is growing research that these connections are good for seniors' health. one study found getting tech smart can improve cognitive abilities. senior centers, libraries and

college extension programs are all helping meet the growing demand for classes around the country. >> if you can't beat them, join them. >> reporter: even if there are bumps in the learning curve along the way. >> there's something wrong. >> reporter: chris jansing, nbc news, new york. >> we'll take a break. we're back in a moment with what the president said today a politician should never do.

president obama was presenting the naval academy football team with the commander in chief's trophy -- something about beating army -- when they presented him with a tricked out specially fitted football helmet, but he didn't take the bait, didn't put it on and at least he explained why. >> here's the general rule. you don't put stuff on your head if you're president. [ laughter ] that's politics 101.

you never look good wearing something on your head. >> the example that comes quickly to mind, michael dukakis in the tank. it has haunted politicians for generations ever since. baseball fights are usually a lot like mardi gras in new orleans. there is a big pile of people, a lot of swinging, but nobody really gets hurt except for last night. vince scully had the call as the padres and dodgers went at it. somebody did get hurt. the dodgers' $147 million pitcher zach grenke got his collarbone broken in the scrum. he and carlos quint on the padres have a history but this was bad. we told you about the youngest player ever at the masters golf tournament this week, 14-year-old 8th grader from china tianlang guan. in a stunning turn of events he was penalized today for playing golf too slowly. experts said this is the first time in the history of the masters that's happened. the one-stroke penalty may mean he doesn't make the cut to continue playing into the

weekend. when we come back here tonight the loss of a comedy genius. the legend being remembered tonight by all the greats that he inspired.

in the business of comedy the professionals loved him. but what mattered most was audiences loved jonathan winters. we learned today the comedy legend died last night at the age of 87. robin williams said today on his twitter account, first he was my idol, then my mentor, and then my amazing friend. winters was a world war ii vet, the king of made-up characters when you think about it. along with soaring creativity came crushing bouts of mental illness. he leaves us with a pile of memories. nbc's kevin tibbles has our look back on the life of jonathan winters. [ cheers and applause ] >> reporter: you couldn't quite put your finger on it, but something about jonathan winters made you laugh. often times even before he opened his mouth. he made the giants of the day -- from carson to martin, even the chairman of the board -- cry with laughter, too.

winters came from dayton, ohio, and got his start when his wife entered him in a talent contest so he could win a new watch. >> my friend jonathan winters. >> reporter: soon it was off to new york and stand-up and "the tonight show," and to hollywood and the wackiest of all road movies "it's a mad, mad, mad, mad world." >> now, fellows, you keep this up and i'm going to get sore. i mean it. >> reporter: gary owens worked alongside winters in "laugh in." >> every time he was a different character he had a different face. >> reporter: he had a genius for characters from maude frickert -- >> give me a little -- oh, isn't that sweet? >> reporter: -- to chester ho y honeyhugger. winters worked with muppets. >> i just can't go on tonight. >> reporter: and "mork & mindy." he did suffer through dark periods, suffering a nervous breakdown and spending months in a mental institution. today this master of the improv was honored in tweets. bob newhart wrote jonathan winters was the king, a true genius.

dick van dyke said the first time i saw jonathan winters perform i thought i might as well quit the business because i could never be as brilliant. he spoke to tom brokaw in 1971. >> i just hope i live to be an old man. i really do. >> reporter: jonathan winters was 87. kevin tibbles, nbc news, chicago. >> that is our broadcast on a friday night and for this week. thank you for being here with us. don't forget, we are back on the air tonight with an all new "rock center" at 10:00/9:00 central. i'm brian williams. lester holt will be here with you this weekend. we, of course, will look for you back here on monday night. in the meantime please have a good weekend. in the meantime please have a good weekend. good night. -- captions by vitac -- www.vitac.com

now. good evening on this friday night i'm jessica aguirre. >> and i'm raj mathai. we begin with the latest on the

investigation of a sexual assault on a 15-year-old teenager named audrie pott. she took her own life days after the attack. it is a troubling story we reported last night. our usual policy is not to identify the victims of sexual assault or suicide. but in this case her parents want her name and face to be shown in an effort to prevent this from happening to anyone else. we have several answers on how the sheriff's department has handled the investigation. we have information about a key piece of evidence. p marianne favro is with us tonight. we begin with monte francis in san jose. >> reporter: the three 16-year-old boys are being held here at juvenile hall. we have learned way back in september they were cited on a misdemeanor charge of sexual battery and released. why did it take seven more

months for them to be charged with felony? three 16-year-old boys in juvenile hall each with two felonies including one for distributing sexual photos of a minor. why it took so long for deputies to make the arrest considered the boys were cited not long after pott's suicide. >> we have to send our computers to forensic labs. >> reporter: audrie pott was at an unsupervised house party and unconscious when authorities say the three teen boys sexual assaulted her and took photos of the attack. the photos were circulated by text messages. audrie pott later wrote i was asleep and they did stuff to me. the whole school knows my life is ruined. a little more than a week after

the assault she took her own life. at saratoga high school emotions are running high. parents and stuchbdents are try to make sense of the unthinkable. >> i would like to see everybody that was a part of what has happened, that justice gets done. in the meantime pott's family wants there to be a law in her name, increasing penalties for those who carry out such attacks. their attorney is asking for students who know anything about the assault to come forward. >> the family's goal is that what happened to audrie never happens again. hopefully her name being out there and her face being seen and her story being told with help increase social awareness. >> reporter: her parents are asking for privacy until this tuesday when they plan to talk to the media. someone from the audrie pott foundation posted a message on facebook accusing the teen suspects of