First of all, this... none of this is your fault. When someone is that desperate and depressed, there is little to nothing that you can do for them, especially if they are not taking meds properly. Please keep this in mind. I've heard many stories of people delaying the inevitable, but if a person has his mind made up, they will kill themselves when they get the chance.
I am so sorry for your loss. Keep talking to people. Talk to your clergy or to a counselor to help you keep your head on straight and to try to at least understand that there is little that can be understood by his actions.
Jasmine was right. Take baby steps. Your Mom is lucky that you live so close to her and that you can be there for each other.
Prayers and hugs are coming your way.