I had s friend when I was 18 (Best friend at the time) who proceeded to take money out of the bank, worked out with his girlfriend, and went for a bike ride. After he got back from his bike ride, he told his girl friend to wait outside while he sneaked into his parents basement window. Three minutes later he shot himself in the face and was killed instantly. By all accounts, it was a pretty normal day, and the girl friend nor any of his friends, myself included had ANY idea he was feeling this way.
There may be something to this story as not all stories are the same, but when it comes to suicide, it's usually the people closest to the individual that have no idea, this poor kids Mom included.