NEUTERING him will help a lot. if she doesn't she is letting him down because I bet you that is where his "aggressive" behavior is coming from and one day something could happen if she doesn't control him. she must do right by him by neutering him. she should have neutered him right when she got him or he wouldn't be so out of control. even with neutering him she needs to socialize him more with people.

she probably got him as a puppy and didn't do anything with him and that's probably why he's out of control. we had a dog come in at the shelter where
I volunteer he was an american staffordshire terrier mix this lady got him as a puppy and did nothing with him and just kenneled him and he was out of control but we adopted him out to a great guy who is taking him to work every day. he works with a constructor company.

pit bulls are supposed to be GREAT with people and by showing aggression towards people is a very, very bad thing. I just hope she gets this poor dog neutered. it really sounds like she shouldn't have a pit bull, period if she isn't going to be responsible and neuter him and control her dog. but please don't be scared of him just because he does that. even if you have to, get him neutered for her. it's really not his fault, it's her fault for not neutering him when she should have years ago.