Updated 1.30pm AEDT

Up to three shooters opened fire at the Inland Regional Centre in San Bernardino, California, a developmental disability facility, on Wednesday afternoon local time (early Thursday morning AEDT), killing 14 people and injuring 17.

“They were dressed in a way that indicated they were prepared,” County Chief Jarrod Burguan said at a press conference, adding that the shooters had long guns, not hand guns. “They came in with a purpose, they came in with an intent.”

The suspects, believed to be armed and dressed in “military style” attire, later fled in a dark coloured car, sparking a city-wide manhunt by authorities and causing ports, local county and city buildings, as well as schools, to be temporarily locked down.

SWAT teams and a bomb squad also swept the premises after a suspicious package was found on the second floor of a building at the centre.

According to KABC, a woman who works in the building texted her father when the shootings occurred: “Shooting at my work. People shot. In the office waiting for cops. Pray for us.”

The Inland Regional Centre is a facility run by the state serving people with developmental disabilities. The centre’s executive director earlier told CNN that she believed the county’s Department of Public Health was having a holiday event there when the shooting happened. This was later confirmed by the San Bernardino County Department of Public Health.

Manhunt: two suspects killed, one detained

Witnesses told CBS News that a dark SUV with two of the escaping gunmen had stopped at an intersection, before a man got out and started firing. Two suspects - one man and one woman - were later killed in a shootout with dozens of officers. An officer was injured during the standoff, but is now in a stable condition. Two rifles and two handguns have been recovered.

A third suspect who was seen running away from the scene has been detained, although it is not confirmed if the person was involved in the shooting at the Inland Regional Centre.

CBS later identified one of the suspects as Syed Farook.

It is not known at this stage if the shooting was a terrorist incident, although federal investigators are involved with the search. There are reports that a county group meeting, and not the health centre, was the target.

Police also served a search warrant on a home in Redlands, California, in association with the San Bernardino shooting.

US has a pattern of mass shooting: Obama

US President Barack Obama has been briefed on the shooting, and has repeated his call for more gun country.

“We don't yet know what the motives of the shooters are, but what we do know is there are steps we can take to make Americans safer and that we should come together in a bipartisan basis at every level of government to make these rare as opposed to normal," he said to CBS news.

"We should never think that this is something that just happens in the ordinary course of events, because it doesn't happen with the same frequency in other countries.

"We have a pattern now of mass shooting in this country that has no parallel anywhere else in the world.”

The San Bernardino shooting takes place just days after three people were fatally shot at a Colarado Springs Planned Parenthood Clinic - the same day (Nov. 27, Black Friday 2015) the FBI recorded the most gun sales in a single day since 1998 when background checks were introduced. 185,345 background checks for gun owners (approximately one every two seconds) were processed.

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