Shooting at California office building kills four, including child

Investigators gather outside an office building where a shooting occurred in Orange, California. Photo / AP

A shooting at a Southern California office building today killed four people, including a child, and injured a fifth person before police shot the suspect, police said.

Shots were being fired as officers arrived at a two-story office building on Lincoln Ave in Orange, southeast of Los Angeles, at about 5.30pm local time, Lieutenant Jennifer Amat said.

"An officer-involved shooting occurred" and the suspect was taken to a hospital, Amat said, but she didn't immediately know his condition.

The shooting was on the second floor of the building, Amat said. Media reports said bodies could be seen on the building's second-floor walkway and in a courtyard.

Amat had no details about the confrontation, what may have sparked the attack or why a child may have been at the building at 202 W Lincoln Ave. Signs outside indicated a handful of businesses were located there, including an insurance office, a financial consulting firm, a legal services business and a phone repair store.

By 7pm, the situation had been stabilised and there wasn't any threat to the public, police said.

Two police officers stand outside an office building where a shooting occurred in Orange. Photo / AP

In a tweet, Governor Gavin Newsom called the killings "horrifying and heartbreaking".

"Our hearts are with the families impacted by this terrible tragedy tonight," he wrote.

Representative Katie Porter, a California Democrat whose district includes the city of Orange, said on Twitter that she was "deeply saddened" by reports of the shooting. "I'm continuing to keep victims and their loved ones in my thoughts as we continue to learn more. My team and I will continue to monitor the situation closely."

A Facebook livestream, posted by a resident who lives near the office building, showed officers carrying a motionless person out and providing aid to someone else, the Orange County Register reported.

The livestream also showed officers taking two handguns from someone who was lying on the ground and providing help to another person. Two other people were led away in handcuffs, the paper said.

The killings were the latest mass shooting in the United States in the last two weeks. Ten people were killed in a Boulder, Colorado, supermarket last week and eight people were fatally shot – including six Asian women – in three Atlanta-area spas the week before that.

Amat said the shooting was the worst in the city since December 1997, when a gunman armed with an assault rifle attacked a California Department of Transportation maintenance yard. Arturo Reyes Torres, 41, an equipment operator who had been fired six weeks earlier, killed four people and wounded others, including a police officer, before police killed him.

The city of Orange is about 48.28km southeast of Los Angeles and home to about 140,000 people.