So enemy minnions attacking them self ?

i was playing irelia, and was freezing the lane, so my creeps died, and the a couple minnions of the enemy lived odly enough i saw purple effects hitting the creeps( i wasnt doing anything, also no sunfre cape or any special aura items)

the minnion kept attacking it self , and killed it self, it was pretty amusing to watch, regardless il see if i can get it to work again, so far it only has worked on enemy creeps on the red side most of the time