It doesn't require "self-defense." It requires a reasonable conclusion on the part of the officer that bodily or serious property harm would result from the criminal's action.
In this case, the officer that fired was hit by the vehicle. Another officer was drug initially because he was holding onto the door handle. In that split second, the officers involved had to make a decision about their next action. The officer that got hit decided that deadly force was called for and used it effectively. He fired three rounds, which would be in line with his training. His intention would be to "stop the action." That is, stop the crime in progress and the criminal committing it.
He would NOT be trying to "disable" the criminal, disarm them, or otherwise do some Hollywood stupidity like wound or shoot their hand or something. He'd aim center mass (upper chest) and fire multiple rounds. That ensures the best chances of hitting the target and stopping the action.