Atleast he or a bystander didn't hose it down with a garden hose..
My father had a lady watering her flowers hose down a rear brake drum on a utility truck he used to drive when it was smoldering/light fire from the drive down a mountain with failed front brakes.
Needless to say, there wasn't much of the exploded drum left.
Sometimes, I guess, doing the 'right' thing is actually wrong :-p

And about your son and the fire hydrant, he shoulda got more inertia behind the automobile. Course then you get to pay for a hydrant
It tis sad regardless...my condolences..