You can train yourself to talk while drawing - a few words might keep you from having to shoot. Of course this is 'situational' - IF you have the time to talk.
Then there is a school of thought (centered on the East Coast) that if you shoot and then shout, the onlookers, conditioned by TV, will all swear you shouted first. But today, with cell phones cameras everwhere, I would not try it. Allways tell the truth, it amazes your friends and confounds your enemies.