Ranged Mobs Infinity Attacking In Large Groups

So in the mod Im making there are a lot of ranged mobs, and at any given point you can have around 20 working on your side. However I've noticed that when all of these ranged mobs attack a multitude of targets, it breaks and after the targets dead they just keep firing in that direction. My assumption to how this is happening is that the mob is targeting something until it kills it, but due to the large numbers in the group something else killed it, there for the others keep firing. I would really like this fixed as currently the only fix for it is to leave the server or get lucky and have all of the shots connect at once on a new target and stop them from firing. If someone could help that would be greatly appreciated!