Hi Jennie and welcome to the board.
Yes suicide is very disturbing. I can only imagine the feelings that you have right now, hurt, mad, sad. You wonder why a person that you loved could do that to himself or to his family. I think sometimes it's selfishness, and yes you would think that person could talk to somebody so that they don't feel so alone in their despair. But I think also that if a person has endured some emotional times, like your grandfather, I'm sure he was very tired. When people get emotionally and physically tired, they want to go to sleep and never wake up. I'm sorry you grandfather had to take the route of suicide.
Hopefully your family will be able to pick up the pieces and become stronger, along from the help that you receive on the board.
Take care Jennie you'll find much comfort here.