I've known 4 people who have killed themselves. 2 hung themselves and two others jumped in front of a train. Only one had previous mental health issues, the rest were out of the blue. I also work with 2 different lads that have had brothers that have killed themselves.
Strange thing is depression, hits different people in different ways. To do that they must be in a really bad place. I wouldn't say it's selfish as who know's what they're thinking?