A 9-year-old boy was the youngest victim of four killed in the mass shooting in Orange, California, on Wednesday. He died in his mother’s arms. She was shot while trying to protect him.

The shooter, identified as Aminadab Gaxiola Gonzalez, knew all of the victims through their work in the real estate industry.

“They were all known to each other,” county District Attorney Todd Spitzer told reporters, revealing that the shooting was not random.

“It appears a little boy died in his mother’s arms as she tried to save him,” he said, adding that the gunman “will suffer and face the consequences.”

Lt. Jennifer Amat of the Orange Police Department told reporters that the gunman was already shooting when officers arrived at the scene on West Lincoln Avenue. According to her, the slaughter began in one of the building’s suites before moving into the courtyard. A firearm was found at the scene.

Gonzalez, 44, of Fullerton, had “issues” with his colleagues at the site, Spitzer said, which was a mobile home real estate office suite. He is now in critical care in the hospital following a “police-involved shooting.” 

Gonzalez secured the gates on the north and south ends of the complex’s courtyard with bicycle-style locks, preventing police from entering, officials said.

Police say the perpetrator was shot through one of the gates, which were then pushed open. Officers encountered the 9-year-old boy who died being cradled by his mother, who was also wounded inside the courtyard. Inside the office complex, the three other victims—two women and a man—were discovered.

“Our hearts today go out to the victims. We pray for one of the victims who is still in the hospital who underwent emergency procedures,” Spitzer said.

Officials said they found a semi-automatic weapon and a bag with pepper spray, handcuffs, and ammunition thought to belong to the suspect at the scene.