If there was an accidental discharge in such a tense situation of arresting someone who resisted while armed, then this is an attenuating circumstance.

Yes but not really. They didn't just execute him obviously but they also completely fucked the arrest up in every way. Not being able to pin him down with 7 people, disarming him without telling anyone and then just unloading without knowing what the fuck even happened.

Now obviously it is easy to judge from a distance but this entire chain of events looked quite unprofessional. I do expect better from supposedly trained law enforcement.