I've been assuming since we heard that this was a set-up of some kind, the sort of 'accident' that swiftly gets arranged once someone's made the sort of wide range of homicidal enemies that Percy acquired for himself.

Arranging for red-haired muggle prey would be easy enough, but possibly insufficient, especially given that the muggles are armed with knives against wands. It's possible the hesitation had some outside assistance, though.

I'm not sure we'd want to suggest that to Molly, however. If anything...it might comfort her to believe that Percy would have balked at murder for sport.