I'm not going to post links to the more graphic footage of these two events but from what I've seen of it the circumstances are horrific. What's more is there seems to be no attempt being made by anyone to assist the victims despite it being pretty obvious that they're no longer much of a threat, if indeed they ever were.
http://www.bbc.co.uk/news/world-us-canada-36732908
I can fully understand why the police in the US are armed but I'm afraid some of them seem to be out of control and far to easily resort to deadly force.