I suspect that that person was coerced or bullied into doing that. Not even a mentally challenged person would would willingly harm themself in that way.
I know a lot of people are looking for youtube fame, but I find that hard to believe.
http://memecrunch.com/meme/7P0SD/why...ious/image.gif
You don't know if it wasn't just poor foresight on the kids part. I'm sure he/she was a little swore, cold and embarrassed at the end but nothing to bad really.