Had a similar situation recently. Neighborhood was nice and quite filled with similar owners/tenants, but one was either a drug dealer or a pimp or both. And the house was right next to my rental.
What I ended up doing were two things. Called the landlord first. They didn't know that such activities where happening. I called the police to create a recent complaint and then the landlord called and confirmed that illegal activities where occurring. Less than a week later, the police set up a sting and raided the house.
Now, in my state (Oklahoma) the landlord could be held liable, so they where happy to listen and act on the situation. Also, the police could not act simply on the few complaints that they received from neighbors. Having the landlord on our side was paramount.
It was all about sugar not spice approaching the landlord and the police. None of the neighbors where ever put in harms way or involved besides the complaints that they had called-in in the past.
I hopes this helps.
