President Barack Obama said it was "absolutely imperative" that police investigate every aspect of the killing of an unarmed black teenager in Florida by a neighbourhood watch captain.
Weighing into the controversial shooting of Trayvon Martin for the first time, Mr Obama said the "tragedy" had made him think of his own two young daughters.
"My main message is to the parents of Trayvon Martin. You know, if I had a son, he'd look like Trayvon. I think they are right to expect that all of us as Americans are going to take this with the seriousness it deserves and that we are going to get to the bottom of exactly what happened."
He was responding to a reporter's question at a White House event to announce his nomination for the presidency of the World Bank.
Mr Obama said he did not want to comment on the specifics of the Martin case, but "I can only imagine what these parents are going through."
"I think all of us have to do some soul-searching to investigate how something like this happened. And that means we examine, the laws, the context, what happened, as well as the specifics of the incident."
Police chief stands aside over handling of case
A local police chief and a Florida state prosecutor both stepped aside over their handling of the case.
The decisions follow criticism and national outrage that police have declined to arrest the alleged gunman.
Sanford Police Chief Bill Lee's resignation, which he called "temporary", failed to appease civil rights and community leaders.
They have called for the arrest of George Zimmerman, 28, who shot the 17-year-old last month and claimed self-defence.
Mr Lee was under mounting pressure for days and suffered a "no confidence" vote from the city commission on Wednesday.
The shake-up at the state level was more surprising as Governor Rick Scott replaced Tallahassee's lead investigator and formed a task force to review Florida's controversial "Stand Your Ground" law.
Police have said this law, which allows people to use deadly force when they perceive danger in any public place, prevented them from arresting Mr Zimmerman.
Mr Zimmerman's father has said his son, a white Hispanic who has disappeared from public view, has been unfairly vilified.
He called him a friend of minorities whose true nature was being distorted by national calls for his arrest and allegations that he pursued Mr Martin just because he was black.
The response to the Martin episode had grown so intense Mr Lee said he had no option but to step aside as "my involvement in the matter is overshadowing the process".
Similarly, State Attorney Norman Wolfinger said he was stepping down "with the intent of toning down the rhetoric".
