A suspect shot by police and one of the suspect's victims were both in critical condition early Thursday in Southern California after a shooting at a business complex that killed four people, investigators said.

A child was among the dead in the shooting, which unfolded in Orange, about 30 miles southeast of Los Angeles, police said.

The suspect was in custody, but was transported to a hospital for treatment of gunshot wounds, after reportedly exchanging shots with arriving officers, the Orange County Register reported.

City of Orange police officers at the shooting scene late Wednesday. (REUTERS/Alex Gallardo)

At least one firearm was recovered at the shooting scene, the report said.

"An officer-involved shooting occurred," was one of the few initial details the Orange County Police Department posted on Facebook. More information from the department was expected later Wednesday evening.

Police arrived at West Lincoln Avenue around 5:30 p.m. PT after receiving a report about gunfire, Fox 11 reported. Investigators said four people turned up dead and a fifth person, a woman, was wounded. Then police faced fire from the suspect, with at least one officer firing back and striking the suspect, according to the Register.

Police said a child was among the dead, and the suspected shooter was wounded. (AP Photo/Jae C. Hong)

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Authorities did not immediately know why the child was at the scene, Fox 11 reported.

The shooting took place on the second floor of an office building but the name of the specific business was not immediately known, the Los Angeles Daily News reported. The building where the shooting occurred houses several businesses, the report said.

Officers were fired upon when they arrived, Lt. Jennifer Amat, a spokeswoman for the Orange Police Department, told the Los Angeles Times.

People nearby comforting each other near the shooting scene. (AP Photo/Jae C. Hong)

Amat described the incident as "a moving situation," the Register reported. The building was a multi-tenant, two-story commercial structure with a courtyard in the center, she told reporters.

A separate Facebook video posted by a nearby resident showed witnesses claiming to see police officers recovering weapons from a person who was lying motionless, and showed other officers leading two people away in handcuffs, the Daily News reported.

The scene was stabilized by 7 p.m. PT and there was no longer a threat to the public, the Orange Police Department told Fox News. Orange is a city of about 140,000 residents.

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Other mass shootings in the U.S. in March included Atlanta-area attacks that left eight people dead, a shooting in Boulder, Colorado, that left 10 dead, and a Maryland rampage in which authorities said a man killed four people and then himself.

Orange police said Wednesday night's shooting there was the deadliest since 1997, when four state transportation employees were killed in a work yard by a former co-worker, the L.A. Daily News reported.