She was actually really offended by this but she does have a kind of androgynous look. Short hair, fairly broad shoulders and a bit chubby around her upper back. She also doesn't dress really feminine.
So when my he got home, he saw her jacket,shoes (which he thought belongs to a guy) and wine glasses on the table. He went into his bedroom and saw us sleeping in the bed together and he freaked out.
He quite literally jumped on the bed yelling something like "I'm gonna kick your ass bro" and hitting her. When he realized she wasn't a guy he calmed down pretty, but even afterward he said he was prepared to kill that guy in there and he didn't seem like he was kidding.
Idk it's not the way I would react. For once I wouldn't be mad at that other girl, but him and second of all I wouldn't react violent in any way. I didn't think he would either, he usually doesn't have a bad temper. How would you react? is it something to worry about?