Investigators said the officer pulled over a driver for a moving violation near Harrison Street and Austin Boulevard.
Body camera video shows the officer walking up to a car, and asking the man, identified as Christian Wallace, to get out.
Investigators said the officer found a gun on him during a pat down and an alcoholic drink in the cupholder.
Dash camera video shows the two getting into struggle over the weapon.
investigators said Wallace broke free with the gun. That's when the officer shot him four times, killing Wallace.
The officer is on medical leave.
Investigators said a gun with a defaced serial number was recovered at the scene.