pissed off my 13 year old brother, how to recognize a trap from him before i get caught in it?

i'm going through a depression stage right now, and he's always a freaking butt-face when his friends are around. so, i was picking flowers, carried them inside to get a string to tie them together... he slaps them out of my hand and says: why the f*** you bringing that sh** in here? then he laughs with his friend. i go outside and cry (i'm going through depression stage of bipolar) mom asks whats wrong and i tell her. i wasnt thinking. and now he believes i should be punished. because i also decided that since he was continuing to be mean that i would tell mom about him spitting BBs all around my grandpa's farmhouse. (we were at his farm at the time) they were my grandpa's best ones. so, he's devious... how do i recognize a trap and not fall for it? he will try just about anything to get me in trouble...