Nightly News | March 19, 2012
>> now to a story in this country that exploded largely to the thanks of social media . a teenager shot and killed by a man carrying a gun. tonight, the dramatic 911 tapes that captured the young man's last moments and the growing calls for justice in a state with a spryi surprising law along those lines. pete williams .
>> reporter: outside a florida prosecutors office today, students demanded criminal charges in the death of 17-year-old tray sean martin walking through a gated community . he was shot by a neighborhood watch volunteer. it all began when he called 911 worried about recent break-ins.
>> this gooks like he's up to now good or he's on drugs or something. he's got his hands in his waistband. and he's a black male.
>> are you following him?
>> okay, we don't need you to do this.
>> reporter: what happened next is captured by 911 calls by neighborhoods.
>> what's going on?
>> so you think he's yelling help?
>> what is your --
>> there's gunshots.
>> that was my baby. and he was pleading for his life. and i just don't understand how that is self defense .
>> zimmerman actually did claim self defense and police declined to arrest him. friends say he's not gun happy or a racist.
>> george is savery congenial person. he never showed up to meetings dressed in camouflage or looked like rambo.
>> florida has what's called a stand your ground law, giving people the right to use deadly force if they reasonably fear for their safety. but some legal experts say the man who fired the shots in this case was the aggressor.
>> he was in a car, he was told to stay in his car. he got out and confronted a young man who was merely walking home from the convenience store.
>> he was carrying only a bag of scand candy and a can of iced tea . social media are buzzing over the case. this twitter page gets a new entry every 20 seconds. prosecutors say the police gave them the case file just a week ago and insist it's still under investigation. pete williams , nbc news,