have drizzle and otherwise, fog for your morning commute. >> good-bye. this sunday night -- national security. but at what price? the firestorm over the obama administration's counterterrorism program. now in an nbc news exclusive, a vigorous defense from the director of national intelligence. watching and waiting. we're live in south africa tonight as concerns grow about the failing health of former president nelson manla. on trial. jury selection begins tomorrow in the case against george zimmerman, accused of murdering trayvon martin, as new questions emerge about the voices on that 911 tape. pain at the pump. gas prices soaring in the midwest. tonight, why the heartland is feeling the pinch. and battle buddies. unconditional love for returning vets living with stressful disorders.

good evening. the apparent source who exposed the government's top-secret collection of phone records has revealed himself. so says the publication that broke the story last week. "the guardian" pulled the covers off an ongoing u.s. intelligence program that's quietly collected the phone records of millions of americans in the name of national security. tonight the self-identified source of that story has stepped forward to explain himself. while the u.s. director of national intelligence in an exclusive interview with nbc news is disputing some of his claims. chief foreign affairs correspondent andrea mitchell spoke to james clapper and joins us from our washington newsroom. >> reporter: good evening. tonight "the guardian" posted the interview with the intelligence contractor who

wants to go public, to that newspaper as well as "the washington post". >> my name is ed snowden. i'm 29 years old. i work for booz allen hamilton as an infrastructure analyst for nsa in hawaii. >> reporter: he says he copied top-secret documents, packed his bags and went to hong kong to share with the guardian's glen greenwald. >> i certainly sitting at my desk had the authority to wiretap anyone from you, your accountant, to a federal judge, or even the president if i had a personal e-mail. >> reporter: his claim is contradicted by what the director of national intelligence told us exclusively on saturday. >> we are under strict court supervision. the notion that we're trolling through everyone's e-mails and voyeuristically reading them or listening to everyone's phone calls is, on its face, absurd. we couldn't do it even if we wanted to. i assure you, we don't want to. >> reporter: why did he do it? snowden says he became

disenchanted while working for the cia and later got hardened while at the nsa. >> i'm just another guy who sits there day to day in the office watches what's happening and goes, this is something that's not our place to decide. the public needs to decide whether these programs and policies are right or wrong. >> reporter: analysts like snowlen use the world's most sophisticated computers to sift through a huge amount of data. even more will be stored in this new facility in utah, all legal since 2008, re-authorized by congress in 2012 and reviewed every three months by a secret court. critics said today more oversight is needed. >> the fact that every call i make to my friends and family is noted, where i am, the length of it, the date, that concerns me. particularly because americans didn't know this. that's why many's calling for reopening the patriot act. >> reporter: before snowlen revealed himself, i asked the

intelligence chief about the leaker. >> this is someone who, for whatever reason, has chosen to violate a secret trust for this country. damage that these revelations incur are huge. >> reporter: can i assume from that, infer that there has been a referral to track down the leak? >> absolutely. we have -- nsa has filed a crimes report on this already. >> reporter: tonight booz allen confirmed he worked for the company less than three months. they said if the reports are accurate about the leaks they are shocked and they would work closely with the authorities on the investigation. tonight while we've learned who the apparent gunman was in the deadly rampage at santa monica community college in california friday, police are trying to determine his motive. this as a fifth victim, a student, has died from her wounds. now the latest on the investigation. >> reporter: this was the moment

police say the gunman entered the library at santa monica college armed to kill. the shooter is a 23-year-old student once enrolled at the college. >> the police department did have contact with this individual in 2006. however, because the individual was a juvenile at the time, i am not at liberty to discuss circumstances of the contact. >> reporter: police are investigating what may have motivated the gunman to go on a calculated shooting rampage. >> i would presume that any time someone puts on a vest, comes out with a bag full of loaded magazines, has a handgun, has a semi-automatic rifle and car jacks folks, goes to a college, kills more people, i would say that's premeditated. >> reporter: it began friday around noon when shots were reported near a house on fire. law enforcement sources say zawahiri allegedly targeted and killed his father and brother inside that home, then hijacked the car demanding the driver take him to the college campus. along the way opening fire on a

city bus. once on campus officials say zawahiri entered the school's library and fired more than 70 rounds. it was there zawahiri was shot and killed by police. some of the 1,300 rounds of ammunition, weapons and gear the suspect were carrying were recovered on campus. today the college community mourned two of its own -- 26-year-old marcella franco, a student, and her father, carlos, a groundskeeper. >> her father was very well liked and respected. >> reporter: the two were driving to the campus when their car was attacked. now counselors have called to help grieve students as final exams go ahead on monday. nbc news, los angeles. in south africa there is growing concern tonight about the failing health of former president nelson mandela. the 94-year-old is in the hospital again, the fourth time since december, with a recurring lung infection. unlike previous hospital visits,

this time public statements about his condition have been less encouraging. nbc's kier simmons is outside the home in johannesburg for us here. what's the latest? >> reporter: this is the first time that nelson mandela's condition has been described as serious, though doctors say he is stable and said to be able to breathe independently. today some of his children and grandchildren visited the hospital where he is said to be being treated for the recurrent lung infection. and his daughter left tonight smiling, saying there has been no news of any improvement from his family or from the south african government since he was rushed to the hospital in early hours of saturday morning. the last time we saw nelson mandela in public he was looking frail. filmed by the south african broadcasting corporation. people were shocked by the pictures but are now told to pray for nelson mandela. one life-long friend has told a newspaper that it is time to let

nelson mandela go. still, many are praying for his swift recovery. in turkey, a tenth straight day of unrest as riot police use teargas and water cannons to battle protesters demanding the government hold new elections. nbc's chief foreign correspondent richard engel is in istanbul tonight. >> reporter: it is the biggest protest movement against prime minister erdowan in his decade ruling turkey. tens of thousands in istanbul alone. feeling more like occupy wall street than egypt's tahrir square. the protests were triggered by plans to bulldoze a park. but when police moved in in force, protests grew way beyond the dispute over urban planning. protesters here say erdowan is trying to impose an islamic agenda and overturn 90 years of secular government in this country.

it is a demonstration about the very nature of turkey and a rejection of erdowan's vision of a islamic democracy. turkey's tradition is embodied by the founder after the republic after world war i. his portrait still hangs in nearly every store. it is on all of the currency. buttered but erdowan has been bringing change, banning sales of alcohol. encouraging women to have large families, challenging abortion rights. the protesters said enough is enough. but erdowan has his supporters, too. he was, after all, elected three times and, under him, turkey's economy has boomed with building everywhere. new bridges, a new airport. erdowan supporters today demonstrated in ankara, sticking with the man critics are calling turkey's new sultan. richard engel, nbc news, istanbul. president obama and china's president jinping wrapped up a meeting today. they moved closer on pressuring north korea's nuclear program. they also reached an agreement

about climate change but divisions remain over china's alleged cyber hacking. the white house saying continued cyber attacks coming from china could strain economic relations between the world's two biggest economies. jury selection is set to begin tomorrow in the trial of george zimmerman accused of murdering of teenager trayvon martin. there seems to be unfinished business that could impact the outcome of this case. it involves whose voice can be heard screaming for help on a 911 call, george zimmerman or trayvon martin. >> reporter: for the last three days -- >> in order to run the test, i had to double up the actual screams. >> reporter: prosecutors and lawyers for george zimmerman have sparred over voice analysis. >> the screams don't match at

all. that's what tells me that, okay, it's not george zimmerman. >> that recording isn't even remotely suitable for comparison purposes. >> reporter: the central question -- exactly who is yelling in a 911 call while george zimmerman and 17-year-old trayvon martin engaged in a physical struggle before martin was shot and killed in february of last year. >> is he yelling help? >> yes. >> what is your name and phone number? >> you just heard gunshots? >> yes. >> how sfm. >> just one. >> reporter: rather than delay monday's scheduled start of jury selection in zimmerman's murder trial, the judge postponed a hearing to determine whether voice recognition experts will be allowed to testify during the trial. >> we'll file a motion. >> reporter: zimmerman's attorney says her decision could be crucial. >> then the point becomes the threshold whether it is going to confuse the jury or assist them. if there is a chance of

confusing them, we shouldn't do it. if it is going to assist them, we should. >> he said you have a problem? i turned around. i said no, i don't have a problem, man. >> reporter: the day after the shooting, zimmerman told police he shot martin after being knocked to the ground and having his head beaten in to the sidewalk by the teen. >> i felt my arm going down my side. i grabbed my firearm and shot it one time. >> he wasn't charged until six weeks later. by a special outside prosecutor. sparking protests about the hesitation of local authorities to arrest him. he's pleaded not guilty to second degree murder. martin's parents contend their son did nothing unlawful that night, he was simply returning to the condo where his dad was staying after buying candy and a soft drink at a convenience store. >> you have george zimmerman who's alive. have you trayvon martin who's not here to tell his story.

of course you're going to blame the victim. >> it could take up to six weeks before a panel of six is ultimately seated. >> george zimmerman has sued nbc universal for defamation. the company has strongly denied his allegations. tonight the man at the controls of the excavator in the philadelphia building collapse that killed six people has surrendered to authorities and is being held without bail the 242-year-old nass multiple counts of involuntary manslaughter, reckless endangerment and risk is a catastrophe. toxicology reports show he had marijuana and painkillers in his system at the time of the accident. when "nbc nightly news" continues on this sunday -- gas prices stable in some places but soaring in others. who's taking the beating at the pump and why. it is that time of year for the time honored tradition of hailing to the valedictorian, all 21 of them, in this case.

the price of gasoline, always a concern at the start of the summer driving season. but now focus has shifted to the midwest where prices at the pump are soaring. nbc's john yang explains why. ridiculous! >> reporter: forget sticker shock. >> $4.60 -- that's a lot. >> reporter: across the midwest, it's gas pump shock. >> what's going on? what's happening? >> reporter: in the heartland, the start of the summer vacation season is seeing a price surge in some places close to record levels. >> that's $4. that makes you feel like you're being strangled. >> reporter: according to aaa, the national average for a gallon of regular is $3.63. but in four midwestern states, the average is more than $4.

in michigan -- $4.23, up 17 cents in just the last week to the highest in the continental united states. some motorists are trying to cut back. >> instead of driving the kids to school, i walk them. >> reporter: analysts blame tight supplies brought on by problems at refineries in the region, including an april explosion and fire at this plant in detroit. others are closed for scheduled maintenance that's taking longer than expected. >> declining number of refineries that meant, that, one, a facility has gone offline and it is a big deal. >> reporter: it could take several weeks for some refineries in the midwest to get running and prices to fall. nationwide some prices are relatively stable and have even dropped in areas of the southeast. >> this summer should not be as bad as last year. >> reporter: but for now, many midwest motorists are frustrated and fuming at the pump. >> there goes all my vacation money. >> reporter: animal lis say the shrinking number of refineries

in the united states makes this kind of regional price volatility more common. john yang, nbc news, chicago. when "nightly news" continues on this sunday, we'll take you to the head of the class where there's always room at the top for more.

it is that time of year when we recognize the hard work of our high school graduates and academic achievement of that one special valedictorian. but as nbc's mike taibbi found out, in some places it is pretty crowded at the top. >> reporter: part of the ritual of high school graduation is the graduation rehearsal. including the speech by the class valedictorian. but at south medford high school in southern oregon, there isn't just one valedictorian.

there are 21. part of a trend that's been spreading nationwide. 34 in one alabama high school. nine in a small ohio school with only 84 seniors. the principal says his 21 medford south stars all deserve the distinction. >> our system is if everybody is a 4.0, everybody is a valedictorian. >> reporter: it is controversial though. one expert in college admissions saying those big numbers dilute the valedictorian brand, raise questions, if not suspicions. >> it does make us wonder at a certain point is there a lot of rigor to the way that school gives out aids? >> reporter: medford's distinguished 21 are being attacked saying all they've done is all they've been asked to numerical perfection. like brea who inhaled college prep courses. >> we all have the value of our own personal education and we know the challenges that we've taken on.

>> luis with no english when he arrived here. >> to make this a accomplishment of being a 4.0 student now is a great accomplishment for myself and my family. >> reporter: and zach snyder, computer whiz. >> we've been in all of these struggles together. our parents and we alike all agree that we've all earned this title. >> reporter: and whether it is one or 21, being a voice for your graduating class matters. i still remember my valedictorian's speech at my k through 6 grammar school. yeah, that's me. it started -- there are seven days of the week, there are seven wonders of the world, there are seven holes in your head, and there are seven plays to lender place elementary school. you had to be there. no jokes on their big night. this is not grammar school, it is high school. >> the only way to be the best in the world is to commit yourself to what you care about and living with purpose. >> reporter: good stuff from 21 seniors who can each say i'm number one -- and forget the as terisk.

history making day at french open today. rafael nadal became the only man to win eight grand slam titles. adding to the drama, a protester held a flare to jump from the stands on to the court and was subdued. yesterday serena williams topped maria sharapova to win her 16th grand slam title. in a moment, when the battle ends and a new one begins -- dogs come to the rescue of some returning veterans.

finally tonight -- helping our combat veterans face the difficult transition when they return home. nbc's dave gutierrez reports on a new kind of therapy that's come to the rescue. >> reporter: at ft. bragg, north carolina -- >> look at that face! >> reporter: -- a rescue operation is under way. dogs at this shelter are strays. or, like zoe, had to be left behind by deployed soldiers. but rescuing them is only the first part of the mission through a program called guardians of rescue, they'll become therapy dogs. buddies for soldiers returning from battle with post traumatic stress. >> quite sure she'll make somebody happy. >> reporter: john wallace knows. a guardian volunteer and former army infantry man in afghanistan, he's recovering from ptsd himself and got his

dog tommy last fall. >> having a dog has completely brought me out of the hell that i was living in. >> reporter: to help others like john, zoe and the other dogs are brought in north carolina to new york for some intensive training. and after three months, zoe is battle ready. >> whenever we send a dog away to its new home it is very bittersweet. >> reporter: bitter -- because they're giving zoe up. but sweet, because she'll be helping others in ways no therapist or family member has been able to. zoe is assigned to army veteran michael metsinger. >> i have been diagnosed with ptsd. i have lower back pain and lower back issues as well. then the migraines. >> reporter: after afghanistan he's had a tough time readjusting to life at home with his fiance. he hopes a battle buddy can ease his pain. >> i'm really excited but i'm nervous at the same time.

>> reporter: this volunteer drives 1,200 miles to deliver zoe. >> i'm traveling a lot for this moment but it is well worth it. >> hi, baby. aw! >> reporter: a dog rescued from a shelter, rescuing a soldier from the scars of battle. >> i just feel great right now. hi, baby. >> today i can say that, know what? mission accomplished. >> reporter: gabe gutierrez, nbc news, venice, florida. that's "nbc nightly news" for this sunday evening. i'm lester holt reporting from new york. for all of us here at nbc news, good night. for our families...

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with more choices and fewer calories... america's beverage companies are delivering. nbc bay area news starts now. good evening, i'm diane dwyer. >> and i'm terry mcsweeney. we begin with a developing story in the east bay, and that is where a limousine burst into flames this morning as a driver was picking up a group of women to take them to a birthday party. the owner of the limo company says the vehicle was idling when it starts smoking. there were four to five elderly women inside, he got them out. no one was hurt. the owner says it was a 2008 lincoln town car limousine that had been regularly inspected. this may remind you, as it did us, to a similar