Not sure

I am not sure where to start.  Last Saturday night my step son got arrested because he lost his temper and hit both me and my 16 year old daughter.  I did not want him to end up in there for very long, I just wanted him to leave the house.  He will now not make it to college.  His mother has been telling him for years that he would never amount to anything.  His father and I have been trying to offset what she says.  At this point I do not know how to help him if there is anything I can do.  His father does not want his son here without him here.  I understand that, but I feel sorry for him also.  He has no where to go now. I hate this position I am in.  I am so confused about what to do.