If you and your neighbors knew that criminals moved into your neighborhood, if you knew for sure that they were committing crimes (dealing drugs, blah blah blah), making your neighborhood unsafe, but you couldn't prove it to the police's satisfaction, and the police were unable or unwilling to do anything about it, no matter how many times you reported them...
What would you do? Would you move, or would you take another kind of action? If so, how far would you be willing to go to preserve the peace and safety of your neighborhood? How far would you go to get rid of the criminal element that didn't belong?