Federal authorities said on Sunday they were in contact with local police investigating the killing of a black teenager last month by a neighborhood watch volunteer in a gated Florida community, an incident that has raised alarm among civil rights leaders.
On February 26, 17-year-old Trayvon Martin was shot and killed as he walked through a gated neighborhood, where he was visiting family. George Zimmerman, 28, who is white, has said he shot Martin in self-defense. Police in Sanford, Florida, about 20 miles north of Orlando, have not charged Zimmerman.
Benjamin Crump, an attorney for Martin's family, said the 17-year-old boy was shot in cold blood. He has said Zimmerman should be arrested and he wants federal authorities to take over the case.
The FBI is "aware of the incident. We have been in contact with local authorities and are monitoring the matter," said Chris Allen, an FBI spokesman in Washington.
A spokeswoman for the Justice Department's civil rights division, which typically investigates incidents involving police, had no immediate comment.
The shooting has cast a spotlight on Florida's so-called "Stand Your Ground" law, which was passed under then-Governor Jeb Bush in 2005 and allows the use of guns or other deadly force as a means of self-defense in public places without first trying to back off from a confrontation.
The law, copied by more than a dozen states, was supported by the National Rifle Association.
Zimmerman's father, Robert Zimmerman, said in a letter to the Orlando Sentinel that his son was a "Spanish-speaking minority with many black family members and friends." He denied that Zimmerman followed or confronted Martin.
"The portrayal of George Zimmerman in the media, as well as the series of events that led to the tragic shooting are false and extremely misleading."
Martin was walking to a convenience store to buy some candy for his brother at the time of the incident, family lawyer Crump said earlier this month. Martin, who lived in Miami with his mother, was visiting Sanford.
Pressure has mounted on federal authorities to take part in the investigation, following last week's release of recorded 911 emergency calls from the incident.
In the months leading up to the shooting, Zimmerman had called police numerous times to report incidents. On February 26, the night Martin was shot, Zimmerman called 911 and said there had been break-ins in the neighborhood and there was "a real suspicious guy" who "looks like he's up to no good."
The dispatcher asked Zimmerman if he was following the person. When Zimmerman replied that he was, the dispatcher said, "We don't need you to do that."
Area residents reported a scuffle in other emergency calls. In one recording - posted by the Orlando Sentinel and other media - a scream could be heard followed by the sound of a gunshot. In another recording, two shots can be heard.
Late on Friday, after police played 911 calls for them, lawyers for Martin's family told a news conference they planned to ask for a meeting with U.S. Attorney General Eric Holder.
Martin's parents told a news conference on Friday they did not trust the Sanford police.
"I feel betrayed by the Sanford Police Department and there's no way that I can still trust them in investigating this crime," said Martin's father, Tracy Martin.
Crump called the 911 calls "shocking."
Sanford Police Chief Bill Lee Jr. has defended the police handling of the case.
"The hysteria, the media circus, it's just crazy," Lee told the Orlando Sentinel. "It's the craziest damn thing I've ever seen, and it's sad. It's sad for the city of Sanford, the police department, because I know in my heart we did a good job."
Civil rights activist Al Sharpton has planned a Thursday rally at a Sanford church.