ORANGE, Calif. >> A gunman who killed four people, including a 9-year-old boy, in a rampage at a Southern California office building knew all the victims and his motive may have involved personal or business relationships, police said.

“This was not a random act of violence,” Lt. Jennifer Amat said today of the attack at a building that housed small businesses in Orange, southeast of Los Angeles.

Aminadab Gaxiola Gonzalez, 44, was identified as the suspected shooter. He was in critical but stable condition. It wasn’t clear whether he was wounded by police or shot himself, Amat said.

Gonzalez, from nearby Fullerton, was staying at a motel in neighboring Anaheim and used a rented car to arrive at the two-story office building on Lincoln Avenue, Amat said.

He chained the front and rear gates to the complex with bicycle cable locks and was spotted on security video wearing a bandana over his face, brandishing a semautomatic handgun and hauling a backpack that contained pepper spray, handcuffs and ammunition, police said.

He targeted Unified Homes, a mobile home brokerage business, authorities said.

Reports of shots fired sent officers to the scene within two minutes, and they exchanged gunfire with the shooter through a gate before the locks were cut, Amat said.

The dead included a 9-year-old boy who was found cradled in the arms of a wounded woman, who was in critiucal but stable condition.

“It appears that a little boy died in his mother’s arms as she was trying to save him during this horrific massacre,” Orange County District Attorney Todd Spitzer said.

A man was found dead inside an office, a woman in another office and a second woman was found on an outdoor landing upstairs.

“The preliminary motive is believed to be related to a business and personal relationship which existed between the suspect and all of the victims,” Amat said. However, she said the precise relationships were still being determined.

A family member identified one victim as Luis Tovar, 50, who owned Unified Homes.

“Our world is shattered,” 28-year-old Vania Tovar, one of Tovar’s five children, told the Orange County Register.

The violence in the city of Orange was the nation’s third major mass shooting in just over two weeks. Last week a gunman opened fire at a supermarket in Boulder, Colorado, and killed 10. A week before that, six Asian women were among eight people killed at three Atlanta-area spas.

Scott Clark, who is owner of Calco Financial that is two doors down from Unified Homes, described Luis Tovar as hard-working.

“He’s there day and night,” Clark said.

Clark left his office on Wednesday, around 4:45 p.m., earlier than usual.

“I must have had an angel from God watching out for me to make me leave an hour before I usually do,” he said.

Clark said he has worked out of the building for about 21 years, and Unified Homes has been in that location for seven or eight years. He said they expanded to a second suite about a year ago, and both offices were on the second level.

Clark said he has seen about 10 people working inside Unified Homes but doesn’t know them well. He said he has chatted with Tovar, sometimes inviting him inside his own office to take a break.

Gonzalez was charged in 2015 in Orange County with cruelty to a child and other counts. It’s not clear if the child that died was his. He pleaded guilty to misdemeanor battery and served one day in jail. All other counts were dismissed, and the conviction was expunged in 2017, said Lauren Gold, spokeswoman for the city of Anaheim.