Please help me..i neeed goood advice!!?!

Please help me..i neeed goood advice!!?

i've noticed the change in him ever since we moved.well we used to be soo close,we'd tell eachother everything.and whatever .you see,hes made a new group of friends.and i know hes been doing drugs.well like 3 people already came to me asking if he has any drugs to sell.he wont let me into his room.but when he has to leave really quick sometimes he leaves his door open and i always see red bandana's and one time i seen a huge pocket knife lying on the floor...his room is mostly red.and he always wears red,so does his friends.could it mean that there in a gang? and im really worried cause if he is in a gang,what if he gets stabbed? what can i do to help him,im really scared for him?? and he doesnt come home for like 2 days at the most,and one time he came home with blood all over his shirt??..WHAT CAN I DO TO HELP HIM???

you need to just straight up ask him what's going on? just say that you haven't really TALKED to him lately and you miss him.