Stress situation and at that close distance, you aren't looking at your gun or your sights, your are looking at your target. It was called reflexive fire when I was in the Army in the mid 2000's. Police might call it something else, but I know they are trained the same way. Basically at close range, you will naturally aim at the threat you see without the need to bring the gun to aim down the sights. Its quicker, and at close ranges, the accuracy is acceptable. Speed is the emphasis at close ranges.
I think the issue here was lack of training. Her being a long term veteran on the force, she was not likely keeping up with training. Sad fact is training for police is barely adequate and heavily concentrated on using a gun. Like most jobs and with most people, the longer you are in a job, the higher likelihood you start coasting and get more complacent. She was probably only doing the bare minimum on already barely adequate training. I think her lack of training led to a mix up, similar to what could happen if you get into a different car with a different ignition system. If you own and are used to a car with a key ignition system in the steering column, and get into a rental with a button the dash, there is a good chance at one point you will reach to twist the key out of instinct and muscle memory. Similar thing could have happened here. She may have thought and wanted to use her taser, but due to her lack of training and diligence, her brain defaulted to what she knew best and she drew her pistol instead. Its no excuse for what happened as it could have been avoided with good training, but I can see how she did not mean to actually kill him. It doesn't change the fact that she should face charges for it and serve time.
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