More like contributing factor; we'll never know what motivated him. But the root cause was a police officer who obviously panicky and as a result probably shouldn't have been a police officer in the first place.
What do you think was the cause?
On what do you base your claim that race was a contributing factor?
Taking a guy straight out of combat, giving him a badge and puting him on our streets is a mistake. I suggest a 2 year "readjustment period" before you are allowed to become a cop after serving in the military.