What a terrible thing! I'm glad you and your wife are okay.
Around here we have tons of overpasses and kids will drop bricks or concrete blocks off the overpass trying to hit cars. There was recently a lady who was nearly killed but survived with massive brain injuries from a block being thrown on her car. It's not a game and kids who get busted doing it are prosecuted.
Any parent who finds out their kids are doing stuff like this should drop kick the little buggers. When I was a kid, we might have spit off an overpass but we surely never tried to hurt anyone.