The part of this that really makes me think is when you thought "I don't think that's going to work" about him going on the hike. That's really tough. In the past there have been times I didn't speak up about a concern I had, then found out that a warning would have been warranted. This is something I think about a lot since becoming a father. There has never been anything in my life before where 99% safe wasn't enough. When you're a parent, 99% safe is a nightmare. Risky situations happen every day. Like staying close enough to the kid on the sidewalk to grab her if the she sees a ball and wants to run into the street for the first time ever. As a parent you have to get comfortable just being a total square all the time, and speaking up about safety even if everyone in the room rolls their eyes. So yeah. It's not your fault, and this person's choice wasn't your responsibility. But you're right, if you were a square and spoke up about safety maybe it would have saved a life. That is a valuable lesson to hold on to.