An 18 year old attacked an 11 year old for NOTHING?

this one guy has issues [rather bad ones] since we broke up from school [in july] he's; pushed an 7month pregnant woman over onto her stomach, pushed an old man over, thrown bricks at a 3 year old, attacked an old man for nothing with building bars, pushed an 11 year old boy over cut his side badly, nearly broke his rib, shouts abuse at ppl for no reason, hit a different pregnant woman, constantly carries wepons [metal bars, bricks, planks of wood] injured his mum, his mum doesnt do anything about it, just tells him to stop it, he does kickboxing twice a week.. hes been reported to the police load of times and nothing gets done, what should we do? hes a danger to himself and other people.