Stunning incompetence

An apparently intoxicated man climbs a tree and refuses to come down. A sheriff's deputy decides to Taser him (Why? the man's not hurting anything. He'll come down when he comes down, if you catch my meaning). The deputy mistakes his Taser for his service weapon and shoots the man, who then decides to climb down. This was obviously not an emergency or a self-defense situation for the deputy, so why didn't he take two seconds to ensure that he was drawing the right weapon? The pattern of decision making in this incident is breathtaking in its depth of stupidity. Hopefully the deputy will lose his job, but he will more likely just get "remedial training".