Aren't players a bit more tightly knit group of people? Especially the "starters". I guess people are never used to thinking about what other people say and think people are joking when they say "oh I would be better off dead".
I can see a practice squad person or someone who doesn't hang around with people slipping through the cracks and no one seeing or talking to them and this could happen a bit easier. I guess it is hard to fathom something like this with no signs or red flags or anything that might have popped up.
Perhaps I am naive