I don't know what your legal remedies are, but my first question is if your neighbor has any family that you could speak to.
I live in the US, but I had a somewhat similar problem with a neighbor. We saw his daughter come by from time to time, so one time we got her attention and shared our phone numbers and explained that we all wanted the same thing: peace and quiet. She was then able to speak to her father and possibly get him to take medication. In any case, things got much better, and when we had issues after that, we didn't go talk to him, we texted her politely to ask that she might do a wellness check and help keep him regulated.
I feel like a lot of people are missing the obvious conclusion that everyone involved here is awful.
Maduro? Brutal dictator. His domestic opposition? Violent fascists. His international opposition? Absolute war criminals.
It's really sad. My primary opinion is that the US needs to leave Venezuela the fuck alone. If you want democracy in Venezuela, you can't get it through sanctioning the population into starvation if they don't vote the way Chevron tells them to. Did Maduro steal an election? Yes! But his opposition at home and abroad isn't mad that it wasn't fair: they're mad because they think it's bullshit for him to steal it after they stole it first!
Get the fuck out and let them actually decide what they want. The US is the clearly the greatest villain in a story with no obvious good guys.