I have the same deal but it's an old guy. Every time I'm outside he goes outside and waters his garden of overgrown weeds and stares. Or he will sit on his porch and glare at the entire neighborhood from 12-8pm drinking beer and getting increasingly abrasive. He tells me I'm supposed to be opening the sewer grate in front of my house and cleaning out the storm sewer so his house doesn't flood during rain which is insane and also not a homeowners responsibility. He has hit my truck, and others cars when we park on the road in front of our houses because "its our fault for parking on his street". He's also sprayed his hose in the windows of multiple people driving by claiming they were speeding (they weren't). Each time the police are called he goes full Dr Jekyl and plays the "I'm just an old lonely man, I don't know what you're talking about, so sorry" or tells them its because of all the nasty "speeders" on our street and he's tired of kids being hit (no kids live within 5 houses of me and no kid has ever been hit by a car on our street). I want to move so fucking goddamn badly because of him honestly there are times I see him outside and I nearly black out from uncontrollable anger. I've warned my gf that if he ever sprays me or the mustang with that stupid fucking hose I'm going to jail 100% that day. Honestly it took me way too long to even type this post as I kept visualizing what I'd do to him and feeling my blood boil.

Shitty neighbors sucks, lawyers is really the only avenue you can explore at this point which is costly and zero guarantee of any change.