WASHINGTON, D.C. -

President Barack Obama is calling the shooting death of an unarmed black teenager in Florida a "tragedy" and says "every aspect" of the case should be investigated.

Obama was asked about the death of 17-year-old Trayvon Martin following a White House Rose Garden ceremony, marking the first time he has commented himself on the shooting that has swept the nation.

The president says he feels sorry for the parents of the suburban Orlando teen and says "every parent in America" should understand why it is "absolutely imperative" that the case is investigated.

"If I had a son, he would look like Trayvon," Obama said in a message he directed to Martin's parents. He also said he thought they were in the right to expect "all of us Americans are going to take this with the seriousness it deserves, and that we're going to get to the bottom of exactly what happened."

The Justice Department and FBI have opened a civil rights investigation and a grand jury is considering whether to charge George Zimmerman.

Zimmerman, a neighborhood watch volunteer, has said he shot Martin on Feb. 26 in self-defense.