At least 14 people were killed and 17 others wounded on Wednesday when three gunmen burst into a handicapped training center in San Bernardino, California and started shooting.
Hours later, police killed one suspect and arrested another after stopping an SUV in which the gunmen escaped. Officers late Wednesday were in an apparent standoff with the others in a neighborhood close to the shooting site.
Television pictures showed a body lying in the street near the SUV with the windows shot out. A weapon was seen nearby.
San Bernardino is about an hour east of Los Angeles. San Bernardino Police Chief Jarrod Burguan told reporters the shooters came to the training center prepared to kill. Burguan said they used what he called "long guns."
WATCH: Video on the scene
Chief Burguan described the shootings as a case of "domestic terrorism," but said he does not know what the motive might have been. He did not say if the dead and wounded worked at the center or were clients.
An FBI official on the scene said investigators do not know at this time if the attack has anything to do with international terrorism.
The facility where the shooting took place, the Inland Regional Center, was founded more than 40 years ago to help people with developmental disabilities.
In comments to CBS television, President Barack Obama said the U.S. has a pattern of mass shootings that has no parallel anywhere else in the world.
He said there are steps that can be taken to make Americans safer, adding that officials in every level of government should come together on a bipartisan basis to make such shootings rare instead of normal.
The two leading U.S. presidential candidates reacted by Twitter. Democrat Hillary Clinton said she refuses "to accept this as normal. We must take action to stop gun violence now."
With details still coming in, Republican Donald Trump said the shooting "looks very bad." He wished good luck to officers on the scene and said this is when police are "so appreciated."
This shooting comes less than a week after a gunman killed three people and wounded nine in a shooting rampage at a Planned Parenthood clinic in Colorado Springs, Colorado. In October, a gunman killed nine people at a college in Oregon and in June a white gunman killed nine black churchgoers in South Carolina.
* This story will be updated throughout the day