Three members of the same family, including a 9-year-old boy, were among the victims of a mass shooting at a California office complex on Wednesday.

Police say Aminadab Gaxiola Gonzalez, 44, locked the gates of the complex and opened fire at the office of Unified Homes, a mobile home broker. Luis Tovar Jr. told NBC Los Angeles that his 50-year-old father, Luis Tovar, who owned the business, was killed. He said his mom, Blanca Tomayo, and 9-year-old half-brother, Matthew, were also killed. “She was super loving, very loving mom,” Tovar Jr. said. “Same as dad—she put others in front of her.” Matthew was found by police cradled in the arms of his mom, identified as Tovar Jr.’s sister Genevieve, who is in the hospital in critical condition.

Authorities say the suspect had business and personal connections to his victims but the nature of the dispute is unclear.