I have asked cop clients I have here, why they don't aim for the legs and their response is it is difficult to target a specific smaller area when someone is charging you with a weapon, so they are trained to shoot the heart area, the torso being the biggest area of the body. It is really tragic this happened but mentally ill or not, he was an implied danger to the cops and could have been a genuine threat to them. Mentally ill people have been known to murder lots of people, they aren't exempt.
There is no excuse for shooting in the head after the torso has been shot several times. That is just murder.
There were bound to be other killings in this region as tempers and emotions run high. Every one is on high alert with their adrenaline at peak levels and that is when knee jerk reactions occur. Until culpability is assigned to that police officer it is going to be an incendiary and exposed situation. Despite the conflicting evidence, surely he can be found guilty of firing too many shots and over kill and charged for that. At least a small arrest would help to pacify and placate the rightfully angered Afro-Americans who are seeking justice.