There was not a black suspect with a gun. The 911 call was about the young white man, who is autistic, and was acting strangely, and had a toy truck that some idiot mistook for a gun.
If someone thinks you look odd then anything you have in your hand is a gun when he calls 9-1-1.
Upon further reading and some reflection, I admit you are right. There was no excuse for this. When deadly force is used, the police better be damned sure they have good reason to do so.
By the way, it turns out my family knows the counselor, Charles Kinsey. His grandmother was our housekeeper when we were little kids. She is still a close family friend. Her kids and grand-kids are all fine people.
This is one clear case where the police are definitely in the wrong.