I have researched this case. The police report (which is woefully incomplete in my opinion) is here;

http://www.scribd.com/doc/293642998/NOEL-AGUILAR-Wrongful-Death-Report

The initial stop was not because he was wearing headphones while riding a bike. It was because when the cops took notice of him he looked at them then he turned and accelerated. When they caught up to him and tried to stop him he ran.

While he was running he was clutching at his waist and one of the cops alerted the other that he had/might have a weapon. So when they catch up to him they are treating him as a threat. The officer on the right already has his gun out when the video starts.

While they are trying to determine if he is armed the suspect is struggling with them and has his hands under him, during this struggle the cop on the right says "It's a gun." The cop on the left then uses his baton to smash the guys arm and then takes the gun and puts it in his waistband.

When he tries to handcuff him the suspect resists and actually has some success, at this point the officer on the right fires and hits the other officer. He never says anything to his partner about discharging his weapon, so the officer that is shot likely assumes the suspect has done it.

The suspect continues to struggle while the shot officer checks to see that he still has his weapon (could also be thinking of drawing it as he reaches back to it a couple more times but does not unholster it) and checks that he still has the suspects weapon (which he then inexplicably drops on the ground and leaves there), then he tries to continue to assist in subduing the suspect. The suspect is still struggling and actually puts his hand on the officer's weapon a few times, whether to push it away or to try to grab it we cant say. The officer on top of the suspect now shoots again.

The other officer probably thinks one of two things - either the suspect is somehow again firing at them, or his partner has determined that deadly force is necessary due to some threat (the suspect is close to gaining control of the officers weapon, has a knife or other secondary weapon). So he pulls his weapon and fires.

I can understand the actions of the shot officer. I cannot fully explain the actions of the other one. It seems like he should have faced AT LEAST some discipline, if not criminal charges.