My daughter has such a dog. It is a brindle pit bull and purely a coward. The problem is that my daughter raised it. I told her to get it trained by someone else but she just couldn't do that. She wanted a sweetheart and she got one. He is quite useless.
Respectfully Thanh, I just don't think the dog's been exposed to strangers in the house, causing a ruckus where your daughter was in a loud confrontation with them.
My pit bulls are terrifed of guns and thunder. The sight of a gun will make my female pee on herself; no joke. She can just hear my son load his 12 guage and she's done for. They are both frantic in a thunderstorm. I give them a benadryl to calm them when the weather gets rough. I do believe my female would do her best to protect us if someone were to invade our home though as she has been thoroughly trained to recognize and react to a real threat. My male would be useless as he is only 5 mo old and hasn't completed "basic" training just yet.