He is three yr old bull terrier he has been attacked by other dogs and now aggressive towards young children when they stroke him or get close the same with dwarf people what's wrong with him please help

I never let anyone touch my dog when out walking; especially small children. Although she is normally well behaved, there is always an unknown factor involved and someone could get bitten.

You must live near a lot of small people. Anyway, get your dog serious corrective training, and you take the training as well.

Small = a threat, another animal, someone at his level, eyes closer to his. This does include children, small adults, even large adults who get down on hands and knees (this is why so many people are bitten in the face after getting very close down).

He needs to be neutered if he isn't yet, and you and he need serious training. Training the owners is most of the process, so that you know how to teach him who's the alpha and that you mean business.

A short leash meanwhile is important, as is keeping a close watch on him at all times. A bite can mean a huge lawsuit and removal/putting down of the dog.