Fourteen people were killed and 17 injured in San Bernardino city of California in a mass shooting yesterday.
Two of the suspects including one female were shot dead by police in an exchange of gun fire hours later. One of the three suspects has been apprehended.
"At this stage we do not know why this terrible event occurred," Obama told White House pool reporters after a meeting with his national security team in the Oval Office.
The Federal Bureau of Investigation (FBI) is carrying out the investigation.
"It is possible this was terrorist-related but we don't know. It's also possible this was workplace-related," said the president.
"What I can assure the American people is we're going to get to the bottom of this and that we are going to be vigilant, as we always are, in getting the facts before we issue any decisive judgments in terms of how this occurred," Obama said.
Noting that it is "fortunate" to have law enforcement and military that keep Americans safe, Obama said "but we can't just leave it to our professionals to deal with the problems of these kinds of horrible killings. Everyone has a part to play".
"It is important for all of us, including our legislatures, to see what we can do to make sure that when individuals decide that they want to do somebody harm, we'll make it a little harder for them to do it because right now, it's just too easy," he said.
