so who taught him the rules to carry?

[TFOGGER]

Warning shots are to be fired center of mass, until the threat has been neutralized. Use of a weapon to deter someone from causing you harm, after they have expressed that intent, does not necessarily mean discharging the weapon. Like Bailey said, use of force is a rapidly changing dynamic situation. Personally, my weapon never leaves the holster unless I am prepared to use it to defend myself, but unlike the sword of a samurai, there is no obligation to draw blood before I reholster my weapon, if the threat is ended and the situation de-escalated.