My guess is he is probably a umbrella cackatoo, they are rather common and easy to get. Cockatoos are very loud birds. They are natural screamers, weather they have enough attention or not. I have a goffin cockatoo, she screams at sun up and sun down, thats natural for them. However the constant screaming is probably from lack of attention, that's not normal. Also cackatoos are notorious for feather plucking, out of boredom. Does he have many toys in his cage to keep him occupied? My guess is probably not. Cackatoos are generally very sweet birds, personally I like them much more than parrots. Mine spends much of her time out of her cage and she has a lot of toys to keep her busy. I would get information on cockatoos and put it into your neighbors mailbox.
Good luck.