They will prey on the weakest for sure. Tree across the road , barking dogs,gun shots, any deterrent will probably send them on down the road to easier pickings.
Unless your the type to slowly pick them off. Say, follow them and set traps in their path or find ways to divide or split the group into smaller groups.
Fortunately, I a the type that likes to look out for others and will be one to tear up a group of opportunists or as I like to place it from the video game Fallout 3 (Raiders).