He was using it. You don't have to pull the trigger to use a gun. Having it out of the holster and ready to go is mostly better if you are expected to contact armed assailants.
The down side to that is if someone had already called the cops and they rolled up on him suddenly. At that point the cops would be more likely to kill him then the bad guys. Being ambushed by the bad guys or shot by the police mistakenly is really the main reason not to go back out there if no one else is in danger.
Given the situation he was acting instinctively and had not considered the above. It is not everyone who moves towards the sound of the guns.