0610 GMT February 17, 2019
SWAT teams were deployed to the scene in San Bernardino Wednesday as police urged the public to avoid the area of Orange Show Road, South Waterman Avenue, and Park Center Circle.
According to police, 14 people were killed and 17 others were injured and the death toll was expected to be moving upwards.
The incident, which involved heavily-armed gunmen, took place at a medical and health center for people with developmental disabilities.
As many as three shooters reportedly opened fire with long guns at the facility at around 11 am local time.
Police said later that two suspects had been downed in a standoff with forces at the site. A cop was also wounded slightly and taken to a local hospital.
The two suspects, one male and one female dressed in military-style clothes, were armed with rifles and handguns, said San Bernardino Police Chief Jarrod Burguan adding, "More people might have been involved in the planning."
Police forces started a manhunt that included a door to door search for some suspect who fled the scene in San Bernardino, situated about 60 miles east of Los Angeles.
A suspect was detained later but it was not immediately clear if the arrest was related to the shooting, which apparently started after a dispute started at an event being held at the Inland Regional Center.
The assailants were said to be carrying explosive which they threw out while being chased.
A bomb squad was also checking the site to make sure no explosives had been left behind.
US authorities were yet unaware if the the shooting was terrorism-related.
A White House official told Reuters that US President Barack Obama was briefed on the matter.
"The president has been briefed by his Homeland Security Adviser Lisa Monaco about the shooting in San Bernardino and has asked to be updated on the situation as it develops," the official said.
Obama later reacted to the incident, saying, mass shootings in the United States have “no parallel” across the globe and calling for stricter laws on gun control.
"The one thing we do know is that we have a pattern now of mass shootings in this country that has no parallel anywhere else in the world," Obama said. "And there are some steps that we could take — not to eliminate every one of these mass shootings — but to improve the odds that they don't happen as frequently."
"It does appear that there are going to be some casualties, and obviously our hearts go out to the victims and the families," he added.