What to do when a friend of yours wants to suicide?

Tweet

I have a good friend which I met about 8 months ago. He was a happy person then, and seemed he enjoyed life. He's an atheist, likes informatics and programming, mostly 3D graphics, he likes (or liked) philosophy, honest and a good friend to have. But things changed a month ago, when he started to have suicidal tendencies. He almost succeeded, but I managed to stop him, with the help of some good friends. But I was the only one to whom he would listen too. I tried to show him that life is worth living, and that he's an important person and loved person (as he believed that no one cares about him, and he's a burden to this world). After that passed, a week ago things started to get worse again. He only talked to me, but with the same calm and smiling behavior, like there's unusual in doing this. Now he is saying that he wants to do this because he can't stand for all the evil in this world, the corruption and suffering, and he keeps believing that there's going to be something better in another life. He even came to "take in consideration the existence of souls and o higher power, or other worlds, but even if they don't, I got nothing to loose" like he used to say. I think I've spent lots of nights with him, talking and philosophizing about life and death. He placed another date, like he did last time, now it's 11th July. I don't know what else to do, it's like I tried to do everything. My girl even had a nervous breakdown because of him, and got really sick, because she always involves in helping people, but in this particular case, she just couldn't take it anymore. What do you think, is he going to do it, or not? If he is, what else should I do? I forgot to mention that he also had problem with drugs (heroin), but I also helped him get over it.