If you are a fast runner or have bad knees, run in a straight line away from the attacker towards cover. The faster you can get away, the fewer shots they will be able to fire. If you are a slower runner and do not have knee trouble, a zig-zag run may be a better option. You may still be hit in this case, but the chances of being hit in a vital area may be reduced. If you can, create visual distractions for the attacker, such as spraying a fire extinguisher.
Again, you should only do this if you have not been seen. If you do this and the cop sees you, they may think you are going for a gun.