What happened is horrible, and there needs to be punishment. In order to actually change things, I think we do need to look at the perceptions and procedures, as well as the very real fears that police have.
The video cam may have been released to make the police's case that, no, the police were not there to just shoot a black person. They walked past an open door which they had been told was "never open" at 2:30 am, saw a bunch of stuff on the floor, which may have indicated an invasion or struggle, and therefore made the call that it was safest to assess the situation further by walking around the property rather than announce themselves at the start. For all they know, someone is being held hostage in there, and they need more information about what's happening (Obviously, it's okay to have your door open at any hour, and it's okay to have stuff on your floor at any time. These aren't reasons to be shot. But the combo may explain the sneaking around and fear)
But I don't see how they will be able to defend the itchy trigger finger and failure to announce who they are before shooting, other than the "feared for my life" response. And sadly, that may work yet again.