Paul Montazer, 37, was actively stabbing his mother in the head and neck on the sidewalk outside her home when officers arrived.
An officer can be heard shouting "Back up! Get away from her now. Drop the knife."
As the suspect appears to get up and run toward the officer, they open fire.
He was pronounced dead at the scene, as was his mother, identified as 72-year-old Parvin Montazer of Irvine.
Irvine police shoot, kill man as he was fatally stabbing his mother