San Bernardino shooting: At least 14 dead
At least 14 people have been killed in a mass shooting in California involving up to three gunmen.
Officers said 17 people were also wounded in the attack at a social service centre in San Bernardino.
The gunmen, wearing military-style clothing and armed with long guns, opened fire at the Inland Regional Center, which helps adults with disabilities.
Witnesses said people locked themselves in offices as the gunfire rang out.
Hours after the attack, police hunting for the attackers riddled a black SUV with gunfire in a residential area several miles away.
San Bernardino Police Chief Jarrod Burguan tweeted: "Suspects are down, one officer wounded. Details still unfolding."
It is unclear if there is still a third suspect on the loose, but he warned residents in the area to stay inside.
The attack took place in a conference area where the San Bernardino County Department of Public Health was holding a social event, said Maybeth Field, the centre's president.
FBI officials said they do not yet know if it was a terrorist attack but local police said it might have been domestic terrorism.
"I think what they are getting at there, following the Paris attacks, is that they do not have any direct suggestion at this stage that this is an Islamist-style terrorist attack," said the BBC's James Cook who is at the scene. "Rather, if it is a terrorist attack it is perhaps some kind if home-grown terrorist attack here in the US."
He said that buses filled with people were being driven away from the scene, while the surrounding buildings remained closed with workers still sheltering inside.
One man received a text from his daughter that said she was hiding inside the building, where she works.
Terry Petit told reporters his daughter wrote to him: "People shot. In the office waiting for cops. Pray for us. I am locked in an office."
President Barack Obama has responded to the shooting.
"One thing we do know is that we have a pattern of mass shootings in this country that has no parallel anywhere in the world," he said.
"There are some steps that we could take, not to eliminate all incidents, but to make sure they happen less frequently."
People were seen being led out of the health care centre which specialises in helping adults with disabilities like autism and mental health problems.
Some were wheeled away on stretchers with medics and police officers in attendance.
Marcos Aguilera's wife was in the building when it happened. He said a gunman entered the building next to his wife's office.
"They locked themselves in her office. They seen bodies on the floor," he told a local ABC News station.
His wife escaped unharmed.
The shooting happened less than a week after a shooting at a Planned Parenthood clinic in Colorado left three people dead and nine people wounded.