This just happened, I had no idea what to do untill his mom came and got him

I ... I want more to the story please. Like what did his mom say? What did you say ?

Our neighbours grand-daughter came in our back door looking or me when she was visiting them

have you tried locking your door?

When faced with stranger danger, drop kicking usually works.

I would slapped some manners into that kid

Adults, please do not be an awkward seal when kids misbehave, assert your dominance and remember you're the alpha (as far as kids know anyway)! If his mother doesn't enforce boundaries in the house, you sure as shit have the right to do so in your property.

I'd call the cops. If the kids isn't being watched and that's neglect. Plus it would really mess up the parents' life, which is fitting since they are not doing their job: being parents.