The chilling 911 tapes from the shooting of Trayvon Martin, the 17-year-old African-American who was killed by a neighborhood watchperson in Florida last month, have raised new questions and frustrations around the case, Slate reported.

Sanford, Fla., police released the eight phone calls late Friday, in which the neighborhood watch volunteer, 28-year-old George Zimmerman, tells the 911 dispatcher that he is following Martin. He explains that Martin is running, but the dispatcher tells him not to follow the teen, the Associated Press reported.

On another call to a non-emergency dispatch number, Zimmerman said that Martin is looking at him, and then claims that Martin "looks like he's on drugs," Ryan Julison, a representative of the boy's family, told ABC News.

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"There's a real suspicious guy. This guy looks like he's up to no good," Zimmerman told the dispatcher on another call. "These a**holes always get away."

Minutes later, however, 911 calls were made to police reporting that the two men were fighting.

"They're wrestling right in the back of my porch," said one caller, according to ABC News. "The guy's yelling for help and I'm not going out."

Someone's screams for help can be heard, along with what sounds like two gunshots.

“I heard someone crying — not boo-hoo crying, but scared or terrified or hurt maybe,” Mary Cutcher, who lives in townhome community where the shooting occurred, told the Miami Herald. “To me, it was a child.”

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"(Zimmerman) was chasing him, he was following him, and my son was afraid," Sybrina Fulton, Martin's mother, told the AP after hearing the tapes. "He didn't know who this stranger was."

Zimmerman told the police he shot Martin out of self defense, and was not arrested or charged for the shooting, Slate reported.

“How can you claim self-defense and you are the aggressor?” Tracy Martin, Trayvon Martin's father, told the AP.

"It is shocking when you hear these 911 tapes," the Martins' attorney, Ben Crump, told Bay News 9. "It was far worse than they thought it was going to be."

The family's attorneys say the family no longer trusts the Sanford Police Department, and have requested that the US Justice Department take over the case, according to Bay News 9.

The tapes were released on the same day Sanford Police Chief Bill Lee said he welcomed a federal investigation, according to Bay News 9.

Reverend Al Sharpton announced through social media that he will be visiting Sanford on Thursday to hold a rally in honor of Trayvon Martin, the Chicago Tribune reported.

The case has drawn national attention and has outraged many residents of Sanford, including many in the African-American community, who have pointed to a history of strained relations between the police department and blacks, the Huffington Post reported.

View all of our Trayvon Martin coverage.