Actually I'll disagree with CrimsonPuma. In my opinion, and as I teach my students, when we do magic we must understand that our actions will bring about consequences. And we are responsible for those consequences, whether we anticipated those consequences or not. So in that sense, if your spell worked itself out by causing injury to those persons so they could not come back to work, you are indeed responsible for that consequence of your spellwork, and for all other consequences that may not have yet occurred because you chose to cast that spell.
That's the problem with spellwork. One needs to be very very clear in one's intention when casting the spell. If you want to simply stop negative behavior then you need to be clear in your casting that such working will not result in harm to any, just a cessation of behavior. Otherwise the spell will simply take the easiest route to its goal, whether that route is something you desired or not.
As for the Rule of Three, don't worry that this means that something horrible will now happen to you. That's not how the Rule of Three works. What the Rule of Three is telling us is that our actions have consequences, and those consequences will come back to effect us physically, emotionally, and spiritually...thus the threefold aspect. But the Universe isn't going to punish you harshly for a single action. Your guilt over what happened is quite punishment enough. But should you continue to do such actions then you will indeed find that there will be negative repercussions.
My point to all this is that it is simplistic to believe that we are let off the hook for our actions simply because we didn't think them through because we aren't. That's deluding ourselves and not accepting responsibility for what we do. This is one of the reasons that many magic users consult their favorite divinatory tool before casting a spell to make sure that that spell isn't going to have some unforeseen and unfortunate result. If you don't, then you will find that magic is a two-edged sword that will hurt you just as much as it can hurt others in your name.