+1,000,000,000 Definitely, get pictures first!

I'm very glad to know your son is OK and not badly injured. Best wishes for a complete and swift recovery of both his body and his mind. On another positive note, this incident might make him use extra caution now that he knows what can happen, although it was clearly not his fault. Sometimes the first accident in life is the wake-up call we need to just be more aware of what is around us, and that awareness can spare us other potential accidents.