it clearly was not accidental. She pulled a weapon and shot him. She may have meant to use a nonlethal weapon but she meant to fire something at him. I have a problem with the use of accidental in that context. Mistaken or negligent works better imho
He had a warrant on him for attempted armed robbery with violence. He was also found to have a gun when he was theoretically under court supervision, and he had skipped his hearings. She had every reason to think he was going back to the car for a weapon, and her (male) partner was unable to restrain him physically. She was perfectly justified in the use of a taser.