Orange County District Attorney Todd Spitzer talks during a news conference at the Orange Police Department headquarters in Orange, Calif., Thursday, April 1, 2021.
After aiding the wounded woman who appeared to be protecting the dead 9-year-old-boy, police searched the complex and found three other fatalities: a woman on an upstairs outdoor landing, a man inside an office building, and a woman in another office building, Amat said. Two officers initially exchanged gunfire with the gunman from outside the gates.
Mr Smith said he heard that repeated twice more by a man's voice and believes it was a police officer speaking. When police arrived on the scene at about 5.30pm, they found the way inside had been blocked.
Police also did not say whether Gonzalez was known by law enforcement or what the relationships were with the victims. She said Leticia Solis and Matthew Farias, a young boy, were also among the victims.
Amat declined to identify the specific business where the gunman first opened fire, but she said the incident began inside one of the complex's suites before moving to a courtyard area.
This past month, two mass shootings - one in Atlanta and the other in Boulder, Colorado - occurred within the span of one week.
The shooting happened at Unified Homes, a mobile home dealer and real estate service.
Amat said officers recovered a semi-automatic handgun inside the complex, along with a backpack containing pepper spray, handcuffs and ammunition believed to belong to the suspect, Amat said.
Amat added that the department could not release the names of the victims at this time because their next of kin have not yet been notified.
"I can confirm the deceased are one male adult, two female adults and one nine year old boy", Amat said.
© Orange Police Department This undated photo provided by the Orange Police Department shows Aminadab Gaxiola Gonzalez, a 44-year-old Fullerton, Calif., who is the suspect in a shooting that occurred inside a business in Orange, Calif., on March 31, 2021.
"Officers immediately approached the building, however were unable to enter the courtyard due to the fact the gates had been locked from the inside", Amat said.
CNN is working to determine whether Gonzalez is represented by an attorney who would comment on his behalf.
Gaxiola, from nearby Fullerton, was staying at a motel in the neighboring city of Anaheim and used a rented auto to arrive at the office building on Lincoln Avenue on Wednesday.
Authorities remained on scene Thursday to complete the investigation.
Spitzer said investigators were there for two reasons: to investigate the mass shooting, as well as the officer-involved shooting aspect of the case, to ensure both objectivity and transparency.
Over the course of his tenure, Spitzer said he had reviewed almost 20 murder cases for whether to pursue the death penalty, but he has never filed one death case.
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.