The LAPD (other than their fine Special Weapons And Tactics unit) is not particularly known for exceptional police work. One of the basic rules of urban combat is that a wall is not a wall until you know for sure it is. A safe background to shoot against is rock/dirt, thick metal, brick or concrete, not drywall. 

The officer who was responsible is a dope - especially because the guy he shot at was not an immediate threat to the officer.  

This would likely not have happened if the LEO on the scene was an L.A. County Sheriff department deputy. They have better training and quality of officers than LAPD. 

My close-combat instructor drilled into me that not only is every shot off-target a lawsuit (or worse) but the only safe background is a safe background. One must assume any "wall" is as thin as tissue paper until you know that it's not. Drywall does not stop bullets any better than a sheet of tissue paper.