How do I handle next door neighbors who shouldn't be there?

[Tiffani Baggett]

I recently purchased a home in Birmingham, Alabama to rent out. I'm currently rehabbing the property. Exterior painting is done. So, there is a house next door that definitely looks abandoned. In fact, my realtor and I were almost sure no one lived there. 

The house is in the tax sale which I requested more info to try and purchase the property to maybe rehab myself or turn over to a rehabbed in the Birmingham AL area. We have the 3 yr redemption period here... Ugh

Anyway, so the painter was confronted by someone out of the house next door stating I need to "cut the limbs away from his roof" 

Now I definitely don't mind this but I'm just wondering, um,... Where did he come from?

I've tried writing the owners of the property and all mail returns undeliverable.