Arnie, you need a pretty large rate of decent to get into VRS and this Helicopter didn't have that until something mechanical happened. I would look at the bushes behind the guy to get an Idea of the wind not the tape that someone is probably holding onto or people passing through a bit further on..
I've got no idea what caused it but it's not VRS or the other classic "no friction on the collective and it's dropped" from a poster above.....Really?