Police in Sanford, Florida, have released a series of 911 tapes from the night an unarmed black teenager, Trayvon Martin, was shot to death by a self-appointed neighborhood watch captain. The case has caused widespread allegations of racial targeting. Seventeen-year-old Trayvon Martin was visiting his father at a gated community on February 26 when he walked out to a nearby convenience store to buy Skittles and Arizona iced tea. On his way back, he was spotted by the shooter, George Zimmerman, who had been patrolling the neighborhood after a series of break-ins. In one 911 call, Zimmerman can be heard pursuing Martin. This is a clip from Zimmerman’s 911 call.

George Zimmerman: “This guy looks like he’s up to no good or he’s on drugs or something. It’s raining, and he’s just walking around, looking about.”

Dispatcher: “OK. And this guy, is he white, black or Hispanic?”

Zimmerman: “He looks black.”

Dispatcher: “Did you see what he was wearing?”

Zimmerman: “Yeah, a dark hoodie, like a grey hoodie, and either jeans or sweatpants and white tennis shoes.”

Dispatcher: “Are you following him?”

Zimmerman: “Yeah.”

Dipatcher: “OK, we don’t need you to do that.”

The Miami Herald reports Zimmerman had taken it upon himself to patrol the neighborhood and had called police 46 times since January 2011 to report suspicious activity or other incidents. Police have refused to arrest Zimmerman, saying they can find no evidence to contradict the claim he acted in self-defense. But frantic screaming can be heard in the background of another 911 tape, leading the family to believe Trayvon Martin pleaded for help before he was shot. The police have said they believe it was Zimmerman calling for help. Listen closely.

Dispatcher: “OK. And is it a male or female?”

Caller: “It sounds like a male.”

Dispatcher: “And you don’t know why?”

Caller: “I don’t know why. I think they’re yelling 'help,' but I don’t know. Just send someone quick.”

Dispatcher: “OK. Does he look hurt to you?”

Caller: “I can’t see him. I don’t want to go out there. I don’t know what’s going on.”

Dispatcher: “Do you think he’s yelling 'help'?”

Caller: “Yes.”

Dispatcher: “All right, what is your [gunshot heard] number?”

Caller: “Just, there’s gunshots.”

Florida college students are scheduled to hold a protest today outside the Seminole County criminal courts to call for Zimmerman’s arrest. Trayvon Martin’s parents are calling for the FBI to investigate the killing.