The footage, taken inside a Pasadena police parking garage, captures a patrol car pulling up behind two officers standing near another vehicle.
One of the officers standing outside is seen quickly drawing his gun and pointing it at the officer in the patrol car. After a few seconds, he re-holsters the weapon.
The video does not show what happens next, but the police chief said the officer seated in the patrol car also drew a gun, which discharged.
The bullet traveled through the windshield and struck the other officer in the shoulder.
The shooting happened last September, but the department released the video Wednesday.
The police chief said the officer who was shot has since recovered and that disciplinary action has been taken.