What to do when your best friend is depressed? please suggestions?! i need more help.?

my best friend hasnt had a very good weekend//week. i posted this in psychology yesterdayy but i need more help. he has been through alot in his family all his life. this weekend he got so mad he punched a wall. i wasnt home to talk to him that day i was on vacation and he did it again monday. i didnt come home til tuesday and i just found out about it yesterday. his brothers make fun of him and he doesnt stand up for himself. obviously he should stand up for himself but it wont do anything ive been over there and ive seen everything that happens. i dont like seeing him depressed but i never know what to say to him. when hes like this he barely talks to anyone but he will talk to me. yesterday he almost broke down in tears and i told him its okay to cry. he doesnt think he should cry about this stuff. i wont be home much this weekend because of the holiday soo i wont really be able to talk to him but me and him can text. obviously it isnt the same but i dont want to see him hurt himself over this. he isnt suicidal i have asked because that was one of my biggest fears. but i dont know what to do to help him or what to say. he does want help but he has problems asking for it. i know he feels alone expecially in his family. the only people he can turn to is his mom if she is home or his friends. he has been to thereapy but none of it has helped. he has days were hes happy then the next he is depressed and want nothing to do with anyone. it upsets me to see him like this. he also has low self esteem and low self confidence. please help?! i would really appreciate it.