ORANGE, Calif. (AP) — A man has been charged with murder and attempted murder in the attack at a Southern California office building that left four dead including a 9-year-old boy.

The Orange County district attorney's office on Friday said 44-year-old Aminadab Gaxiola Gonzalez was charged with the attempted murder of two police officers after shooting at them when they reached the scene.

Police say Gaxiola opened fire Wednesday at the office building in Orange and knew the adult victims, either personally or through business.

A specific motive for the attack is unclear.

Gaxiola is expected to be arraigned Friday from the hospital, where he is in critical but stable condition. It was not immediately known who his attorney would be.