As he pulls it out of the drawer and it just happens to go off and also just happens to be aimed right at her.

Also worth noting that he shot her with a Glock. Glocks have a safety built directly into the trigger, which needs to be pressed before the trigger will move. It’s the blue part of the trigger in this image:

In terms of “just happened to go off”, a Glock is just about as safe as you can get. The dude 1000% pulled the trigger, because that sprung lever needs to be pressed before the trigger will even begin to move.