The killing of an unarmed black teenager by a mixed race man in Florida has provoked an outcry, with many critical of the police handling of the case.
17-year-old Trayvon Martin was visiting his father in an Orlando suburb.
The boy was carrying a bag of sweets and a can of soft drink as he walked through the gated estate.
It was raining and he had his hood up. A neighbourhood watchman, George Zimmerman, thought he was acting suspiciously and called the police.
After an altercation, the 28-year-old then shot the boy dead. He claims he was attacked and acted in self-defence. Eyewitnesses have given conflicting accounts.
President Obama clearly sympathises with the teenager and his family.
“My main message is to the parents of Trayvon Martin. You know, if I had a son, he’d look like Trayvon. And, you know, 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’re going to get to the bottom of exactly what happened,” he said.
Protesters have held rallies, demanding to know why police failed to arrest Zimmerman or investigate properly.
More than a million people have signed an online petition started by Martin’s parents.
“We really appreciate it. We want justice for Trayvon,” said his mother.
With the president’s intervention, the case shows every sign of growing into a major national controversy.