He sounds like some of the kids that I test for ADHD or similar problems. Many of these kids also: are abused (they are hard to discipline and if you don't understand that they can't help themselves, it's tempting to really let them have it), depressed (which in children can be expressed as aggression), sure that the world hates them because they always get yelled at and they don't really understand why.
Check for the bruises, if none, try to talk to the parents about the urgency of getting him help. Keep in mind, some hyperactive kids have a lot of bruises from not tthinking and crashing into things. My sister fell into this catagory. You can call social services and ask anonymously for advice. I have when I worked in the States in CA. There are probably a LOT of things going wrong around this little boy. Good luck. HHUUUUGGGGSSSS!