Officials work outside the scene of a shooting, Thursday, April 1, 2021 in Orange, Calif.
Lt. Jennifer Amat, a spokeswoman for the Orange Police Department, identified the suspect as 44-year-old named Aminadab Gaxiola Gonzalez and revealed what she described as that person's ties to the victims at a press conference.
Among the victims of the "horrific massacre" Wednesday afternoon was a 9-year-old boy who was found cradled in the arms of a woman believed to be his mother, Orange County District Attorney Todd Spitzer said.
Another person was wounded in the incident and the suspect was hospitalized, authorities said.
The bloodshed in Orange, California, about 50km south-east of central Los Angeles, marked the third deadly mass shooting in the United States in less than a month.
Police identified the suspect in a Wednesday shooting that killed four people in Orange, California.
"Horrifying and heartbreaking", said California governor Gavin Newsom on Twitter. He said, "Our hearts are with the families impacted by this bad tragedy tonight".
Amat had no information about what may have prompted the attack. "An officer involved shooting occurred", said the post, which was filed shortly after 7 p.m. 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 fix store.
People gathered outside the building after the shooting hoping to get word about loved ones. Paul Tovar told KTLA-TV his brother owned the company.
"He's not answering his phone, neither's my niece", Tovar said. "I'm pretty scared and anxious ... right now I'm just praying really hard". He was in the back of his house when he heard a volley of three gunshots, then a volley of three and a final volley of four.
Orange is about 30 miles (48 kilometers) from Los Angeles and home to about 140,000 people.
Amat said on Thursday that the shooting happened at a business called Unified Homes.