It's difficult to comment on this specific case as there is not enough information. ...snip... There is just not enough info to give an informed opinion but I'm going for unjustified in this instance. Police forces should at all times be in the position to use incapacitating but non-deadly force. These officers do not appear to have had the tools at their disposal (Taser) that would have allowed that.
Given the same caveats I pretty much agree with what you have posted.
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I simply think the police should be constrained in the same way the rest of us are i.e. the only time when I think police are "justified" in killing someone is when someone's life is in imminent danger (or serious injury), otherwise they should be legally constrained to use other solutions.