How do I designate who/what the Event/Target entity is?

So I've made a giant angry cow/bull mob. It's nasty and chases you, but still not quite dangerous enough. I happened across the procedure block for setting something on fire, so I thought perfect! When it's angry having the bull erupt into flames is just the right amount of OMG! Buuuut I've done something wrong with the procedure setup, instead of setting the bull on fire when its mad it's setting ME on fire! I suspect the procedure is targeting me, because I have it set to only happen at normal and hard difficulties, when I triggered the failsafe of changing the difficulty to easy it extinguished me... the procedure is linked to the bull but it's effecting me, how do I change or designate the bull as the event/target entity? Thanks!