WASHINGTON (AP) -- President Barack Obama called the shooting death of an unarmed black teenager in a Florida suburb a "tragedy" on Friday and said that "every aspect" of the case that has rallied civil rights activists should be investigated.

Speaking in personal terms, Obama expressed sympathy for the parents of 17-year-old Trayvon Martin, who was shot on Feb. 26 in Sanford, Fla., a suburb of Orlando, by a neighborhood watch volunteer who said he was acting in self-defense.

"I can only imagine what these parents are going through and when I think about this boy I think about my own kids," Obama said. He aimed his message at Martin's parents, saying, "If I had a son he'd look like Trayvon. I think they are right to expect that all of us as Americans take this with the seriousness that it deserves and we're going to get to the bottom of what happened."

Obama said that "every parent in America should be able to understand why it is absolutely imperative that we investigate every aspect of this and everybody pulls together, federal state and local, to figure out exactly how this tragedy happened."

The Justice Department and FBI have opened a civil rights investigation and a grand jury is considering whether to charge George Zimmerman, who acknowledged shooting the teen but said it was self-defense. Martin's parents, civil rights activists and others who have rallied to the cause say they won't be satisfied until Zimmerman is arrested.

Police Chief Bill Lee stepped down temporarily this week to try to cool the building anger that his department had not arrested Zimmerman. Hours later, Gov. Rick Scott announced that the local state attorney, Norman Wolfinger, had recused himself from the case in hopes of "toning down the rhetoric" surrounding it.

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