Very sad. :(
I don't think you can make them believe it, Clay. The ones who think they're invulnerable don't listen to their parents, IME, because they think we're just fussing. My DS used to say to me all the time "You worry too much. Nothing's going to happen. Even this poor boy's last words were "I'm not going to die"... :(
I think that what it takes, frighteningly, is for something like this to happen to someone they know. My DS was on the fringes of something 18 months ago that led to one boy being killed, another almost dying, and two people going to jail for murder, attempted murder and manslaughter. They were the people who were selling drugs to young people (14-18) in our area - including my son. It was a wake-up call for him and several of his peers - they finally realised it could have been any of them - and several of them made positive changes as a result. But it is truly awful that someone actually had to die before those boys realised the risks they were taking. :(