All the times he bit people:
1: He's bit Gage -my bros stepson- 3 times, each hard enough to bleed and scar. Though we are not sure if Gage was rough housing him like usual, because he was alone and wouldn't admit to it.
2: He was under the bed and chewing his toy when my bro reached under and tried to grab it and he bit him.
(After this my bro was gonna put him down but gave him to us. He also bit my sis when they originally got him because she touched him while he was sleeping, but it was not a bad bite. Also every time a male walks in he doesnt really know he barks a lot and growls.)
3: He was sleeping when I walked by and he jumped up and bit me. Though it was mainly a nibble and didnt hurt at all. When he realized it was me he let go immediately.
4: He bit my Uncle and made him bleed a little when he walked in the door.
5: My girl cousin came in today -hes met her multiple times and had no problem- and he sniffed her and walked away and she went to reach and pet him and he jumped and bite her hard enough to leave a bad mark and draw lots of blood. As soon as my mom yelled at him he let go and backed away.
He's only 1 and a half years old, growing up my brother rough housed him a lot. But hes usually very sweet and playful and he only gets riled up with knocking, and seeing things outside, or hearing car doors. Anytime someone trys to harm us he jumps and defends us. We asked the vet and he said it was because hes scared. What should we do? What does this mean?