What the heck did he do??? Was he solo and his e-brake failed? OR did some arch rival pop the brake as he was unhitching the boat? - OUCH! That is a tough way to learn how to (or better yet, how NOT to) launch / trailer a boat...
There was a recent incident (think a year or two ago) at Salmon lake where an RV reared down into the water at the boat dock...
the launch there is really steep. I was out on the river when it happened. but possibly an E-brake failure with a manual trans, or maybe just a woman driver?