A mob-sentinel who returns to the spawning site after killing a hostile mob

Hello everyone!

I have a question. I created a NPC, which kills hostile mobs. But obviously, when I spawn him, he walks all over the territory and subsequently goes very far.

I have such an idea. And I would like to ask you to help me. I want when I spawn a NPC, he stands still until he sees a hostile mob. As he kills it, the NPc should go back to where I originally spawned it.

(Who used the Custom NPS mod and created there guards should understand what I'm talking about)

Obviously, this is most likely done through "procedures" and most likely can't even be done. But maybe someone has tried it...