My boyfriend and i got caught by my older brother ?

ok to start everyone in my house was gone and had planned on being gone all afternoo until 8 well i was alone so i called my bf adam over and we went up to my room to watch the hangover (again) and about half way through the movie he started kissing me and before i knew it he was on top of me grinding on me and making out with me we had not intentions of sex we have already talked about that but my brother comes running up the steps and without knocking barges into my room and goes what tha f*ck get the hell off my baby sister then he said I WILL TALK TO YOU ABOUT THIS LATER he was pissed i know he wont tell mom because i have to much dirt on him i know that he was being protective but god why did he have to freak out so bad and what should i say to him to make him feel better about this