Family on Thursday identified the victims as Luis Tovar, his daughter Jenevieve Raygoza, Leticia Solis and 9-year-old Matthew Farias, who was found cradled in the arms of a woman believed to be his mother.
The 9-year-old boy's mother Ismeralda Tamayo is believed to be the lone survivor of the shooting. She remains in the hospital in critical condition.
The Orange Police Department on Friday officially released three of those names. Raygoza was 28 years old and Tovar was 50.
The fourth victim, presumably Solis, has not been officially identified. The family of Leticia Solis told Eyewitness News they are devastated by her killing and request privacy.
A GoFundMe page has been established to help Farias' family with funeral costs.
In a statement, the Santa Ana Unified School District said the community was "heartbroken" to hear the news of Farias, who was a third grade student at Hoover Elementary School.
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The suspect was identified as Aminadab Gaxiola Gonzalez of Fullerton. Gonzalez remained hospitalized in stable but critical condition on Thursday. It was unclear whether he suffered a self-inflicted wound or was shot by police.
Authorities say the suspect knew all the victims either through a business or personal relationship.
At a Thursday morning news conference, police added the shooting, which was first reported around 5:25 p.m. Wednesday at 202 West Lincoln Ave., was not a "random act of violence" and believe it was an isolated incident.
Police said that apparently before opening fire, the suspect chained shut the gates to two entrances, delaying police from getting inside.
Police recovered a semi-automatic gun and a backpack with pepper spray, handcuffs and ammunition.
Authorities released a photo taken from surveillance video that investigators said showed the armed and masked gunman during the shooting rampage. He is seen carrying an apparent firearm and backpack in the image.
Authorities say the business associated with the victims is Unified Homes, which is described on its website as "a full-service manufactured home dealer and real estate company which specializes in Orange County."
Although investigators say the shooting was not random, a motive remains unclear.
The Associated Press contributed to this report.