The problem is escalation. You fire your shots in self defence, they back off an extra 50’ and call in a “shots fired, officer needs assistance” call and suddenly 4 APCs, 20 cruisers and 2 helicopters are surrounding you. Cue sounds of 50 cal freedom suppressors being fired. And because you shot at them even though by the time its all over your body looks like a pile of spaghetti the shooting will be justified with barely a hearing involved.