http://www.soccerclips.net/videos/barcelona-v-arsenal-van-persie-red-card
There was about a second between the whistle going an van Persie taking the shot, that's more than long enough for him to stop, if the game was still going on there's no way he would have shot like that, it was a perfectly fair yellow card. van Persie does this all the time, and I was quite happy to see a referee finally give him a yellow card for it.