My general impression is that most agencies would prefer you stay out of it and let them handle it. I'd give the non-emergency number at your local police agency a call and ask what they suggest you do. keep in mind that regardless of what you do, if you do take action, it's possible for the bad guy to give you quite a bit of grief.

Keep in mind that online renters insurance is available at very low cost. While you are currently risking potential theft issues, longterm there are other potential problems, such as a fire. All of these losses can and should be covered.

Nothing is worth risking your life or a neighbors life for, and I think you are primarily worred about theft. Of course if you are worried about the female neighbors, I'd again defer to the local police agencies to see what they suggest. KEEP IN MIND MANY SEX OFFENDERS COMMITTED LESS SERIOUS CRIMES THAN YOU MIGHT EXPECT. Rapists and child molestors are a very small percentage of sex offenders and my experience is that they usually end up in jail.

For me, most "things" can be replaced. Let the insurance kick in. Potential threats to family and friends might be handled different.