What would you do if your neighbor was sitting in your living room when you walk in the door, with no explanation?

My neighbor 2 houses down, walks my dog and hangs out at my home. Tonight I went to drive some girls to celebrate for graduation and came home to the guy and his gf hanging in my house, with the door locking me out. I’ve already written him a note about crossing boundaries. I’m livid.

Who is their right mind, thinks it is alright to go in someone’s house and chill when the owner isnt there??