Find a cab driving around with a passenger. This may also work with other cars and your gang members. Take the car and drive it into water (best done at the Glen Park area in Los Santos). Get out of the car as it is driving into the water and go ashore, so you can see the passenger trying to swim. After a short while he or she will be dead, still are trying to swim. Aim at the person and the target will appear black, indicating that the person is dead. Fire at the car's gas tank to make it explode and send the person flying ashore. They will now run around for awhile, then act like a normal person. However, they will be invincible and will still be targeted black.