SANFORD, Fla. -

After listening to recordings of 911 calls, the family of a black teenager fatally shot by a white neighborhood watch volunteer say they're more convinced than ever that the shooter should be charged.

LISTEN: Raw 911 calls

Attorney Benjamin Crump, who is representing the family, told reporters outside Sanford City Hall that 17-year-old Trayvon Martin's parents both broke down and cried as they listened to the recordings.

"They are completely devastated, and they are in unbelievable grief," Crump said.

Police agreed to release the recordings Friday afternoon after initially refusing to make them public and Martin's parents sued to have them released. It's not clear when exactly the calls will be released to the public.

Officials released a total of seven 911 calls. All of the callers described a single shot.

"There is somebody screaming outside," one female caller said, as an unknown male voice can be heard crying in the background. Then a shot is heard.

A male caller described a physical altercation between Martin and the shooter.

"I just heard a shot right behind my house," The caller said. "They're wrestling right behind my porch. The guy is yelling 'Help.' I'm not going outside."

Sanford police faced criticism at a news conference earlier Friday for its investigation into Martin's death, including remarks the father of Martin who said he felt "betrayed" by police as he pushed for the FBI to take over the investigation.

Tracy Martin and Sybrina Fulton, the parents of Trayvon Martin, spoke to the media at attorney Natalie Jackson's office. They were joined by Mary Cutcher, and her roommate, who are witnesses in the shooting.

Martin, 17, was shot and killed last month by neighborhood watch leader George Zimmerman, 28, while Martin was visiting family in Central Florida. Zimmerman was questioned by Sanford police but has not been arrested.

Sanford police Sgt. David Morgenstern said the department stands behind its investigation but welcomes another agency "to scrutinize and review" the case.

Also on Friday, Brown called for the U.S. Department of Justice to investigate the case.

Check back with Local 6 for more information.