SANFORD, Fla. â€"  DEVELOPING: George Zimmerman took the witness stand Friday at his bond hearing, telling the parents of Trayvon Martin, "I am sorry for the loss of your son," but standing by his claim that he killed the teen in self-defense.

Zimmerman, who is charged with second degree murder in the shooting death of Martin, made the brief statement during Friday's hearing over whether he should be released on bail while he awaits trial.

Zimmerman told Martin's parents, who were present in the courtroom, that he did not know that Martin was 17 and that he was unarmed during their February confrontation in a central Florida neighborhood.

"I did not know how old he was," Zimmerman said. "I thought he was a little younger than I am. I did not know if he was armed or not."

Zimmerman's wife and parents testified by phone earlier that he is not a violent person. Zimmerman's father told the courtroom that his son always "turns the other cheek."

But prosecutors asked Zimmerman's wife, Shellie, about two incidents they said showed he has a violent nature. In one, Zimmerman took anger management courses after an undercover police officer said Zimmerman attacked him. A former girlfriend also once accused Zimmerman of assaulting her.

Zimmerman appeared at the hearing wearing a suit but in shackles. He surrendered his passport to the court at the start of the hearing. 

The hearing got under way just hours after ABC News released an exclusive photograph that claims to show the bloodied back of Zimmerman's head. The photo, reportedly taken three minutes after Zimmerman shot and killed Martin, appears to support Zimmerman's claim that Martin had bashed his head against concrete.

Click here to see the photo released by ABC News

Legal experts say factors in Zimmerman's favor include that he has ties to the local community and that he doesn't appear to be a flight risk since he turned in voluntarily after second-degree murder charges were filed against him last week. He also has never been convicted of a crime, which would indicate he doesn't pose a threat to society.

"Although it's not routine for people charged with murder to get bond, they do get bond, and I think there is an excellent argument to be made in his specific case for him to be released on bond," said defense attorney Randy McClean, who practices in Seminole County, about 15 miles northeast of Orlando.

A spokeswoman for special prosecutor Angela Corey's office said Thursday she wouldn't comment on whether Corey would object to Zimmerman being released on bond.

Defense attorney Mark O'Mara indicated he would ask that Zimmerman be allowed to leave the area, if he is granted bond, because of concerns about his safety. Circuit Judge Kenneth Lester was assigned the case Wednesday after a previous judge recused herself because of a potential conflict of interest.

"Normally, the conditions are that you stay local. I think that is going to be difficult," O'Mara said in an interview with the Associated Press. "I think nobody would deny the fact that if George Zimmerman were walking down the street today, he would be at risk. That is a reality."

O'Mara has said he would prefer that Zimmerman be released so he can assist in building a defense case.

The judge would have discretion to allow Zimmerman to live elsewhere along with a number of restrictions such as a curfew, regular reporting requirement and possibly an electronic monitoring ankle bracelet, said Florida International University law professor Joelle Moreno.

O'Mara said he would ask for assistance from law enforcement. Kim Cannaday, a spokeswoman for the Seminole County Sheriff's Office, said she couldn't comment on what security procedures will be in place for Zimmerman if he is released. The sheriff's office does have the ability to monitor defendants outside the county if a judge requests a GPS monitor to be used as a condition of release.

Zimmerman is charged with second-degree murder in the 17-year-old Martin's death during a Feb. 26 confrontation in a Sanford, Fla., gated community. Martin was walking home from a convenience store when Zimmerman spotted him from his truck and called police to report him as suspicious. Zimmerman has claimed self-defense under Florida's "stand your ground" law, which eliminates a person's duty to retreat under threat of death or serious injury.

The lack of an arrest for 44 days spurred protests nationwide, several in Seminole County, in which participants chanted and held signs that said, "Arrest Zimmerman Now!" Anger over a delay in Zimmerman's arrest led to the Sanford police chief stepping down temporarily and the recusal of the prosecutor who normally handles cases out of Sanford. Sanford city officials were holding a town hall meeting Thursday to address some of the residual anger from the case.

The Associated Press contributed to this report.Â