Don't worry, the city will protect you
Strangely, NYC doesn't take that position in court. A madman kills four, NYPD manhunt follows. Two officers are in a subway cab when the madman enters the car, and they do nothing to stop him. He stabs a passenger right next to them, who in turn wrestles him down, at which point the NYPD folks finally emerge. Now he sues the city, and it of course argues that it has no legal duty to protect the citizenry.