Being a police officer is a difficult job. Not every one has what it takes. This guy certainly does not. He shot at his fears. An unarmed man opened the door and the officer freaked. Any time a police officer shoots an unarmed citizen, who is not a threat, it is proof they are not cut out to be a police officer.
This shooting is not typical since most of the time the officer doing the shooting fires multiple rounds or even empties his magazine into the person. In shootings where other officers are present, they most always fire their weapons also. This shooting is more like an accidental discharge.
The standard police response police make in these mistake shootings is, "I was fearful for my life" and he reached toward his waistband".
What more do you need. A dead unarmed American citizen who simply opened his door when the police were at the wrong house for a prank call is all I need. No weapon, no crime, and yet we have another body on the ground due to police error. The guy is not cut out for the police force.