White House spokesman Josh Earnest said the attack by two gunmen was "still under investigation," adding it's "too early to say at this point" whether Islamic State fighters were responsible.
"This is still under investigation by the FBI and other members of the intelligence community to determine any ties or affiliations that these two individuals may have had with ISIL or other terrorist organizations around the world," Earnest said.
Earnest cautioned that extremists sometimes make claims of responsibility for propaganda purposes "to try to communicate with individuals around the world, including inside the United States.