This will work on any level. During Take A Ride mode when the cops are not after you, pull out your gun and start shooting people. Once you see a cop coming towards you on your radar, quickly put your gun away. The car will stop in the middle of the street and the two officers will get out. One of the officers will stand by the car while the other wanders off. Keep both of them in sight for about a minute (without pulling out you gun or stealing a car). One of them will start shooting at people for no reason. Sometimes both of them will shoot.