How do you deal with cutters?

My brother is not me we argued last night and i put my hands on him i choked him.. i have bipolar disorder.and he did something to get me mad after a while we exchanged words him yelling at me about our past because ive done this before let my anger get the best of me and hurt him he cut himself in retaliaition, but in the past we talked it out, exchanged our feelings and i cried told him i loved him and that im going to change i failed him yesterday we did the same thing but this time my friends was over he ran downstairs to see him cutting himself one freaked out and ran, the other knocked out the knife and asked him wtf are you doing he was sad because of bullies not to mention his own brother being one. Im so ashamed and i dont want this to happen again, please i dont want this to escalate to suicide hes thought of it before i cant even think of it what do i do/say?