Parents will do the most fucking stupid of things just because their offspring gets angry. Calling 911 because your child is angry does nothing to help with the problem. Honestly, parents these days are resorting to the stupidest shit in the history of parenting.
There needs to be a "no angry child" policy for police. Honestly, it's not going to solve the fucking problem. Fucking idiots.
Also, your mother is a dumb bitch if you didn't get the point from the above. Your brother is completely fine, getting angry is natural, there is nothing to restrain such emotion. He's not going to get admitted to a mental hospital for "being angry". No person will. Ever.