Hello emmajune: I see this is your first post here on PC. Welcome to Psych Central.

As a person who has done (on 2 different occasions) what your friend did, & without going into a long dissertation on the subject, I think all I can say is we never really know what's going on in another person's mind.

You wrote: "What is so bad that he thought he couldn't tell us and puts his own life in danger like this instead?" Of course I have no idea what the answer is to this. Only your friend knows for sure. (It could be he doesn't really even know himself.) But what I can say is that, in my own case, it has always been true that if I was rational enough to call someone then the likelihood was I wasn't really in danger. But if I was really in danger the last thing I would be likely to do was to call someone. That's simply the reality of my circumstances. Perhaps your friend's situation is similar?

Being on antidepressants is one thing. And sometimes it's an important thing. But talking things through at-length & in-depth with a mental health therapist or psychologist can be equally important. So I hope your friend receives the help he needs & that you find having come here to PC to be of benefit. My best wishes to you all.

P.S. Here's a link to an article, from Psych Central's archives, that discusses some of the reasons behind suicide attempts plus a link to an article that reviews common signs someone may be suicidal:

Suicide: When It Hurts Too Much To Live

Common Signs of Someone Who May Be Suicidal