Your post ignores too much.
First, if you are harboring a murderer and he takes you hostage, it is only your own fault. Not the police.
Second, if a killing spree is underway (Columbine), police should not wait outside for the killing to end, they should intervene.
The problem most FReepers have is that the police use aggressive, over-the-top force when surrounding and knocking would be sufficient and then those same police will standby outside and do nothing while a gunman (gunmen) kill innocents inside a building.
Godbee didn't say if the suspect in Blake's slaying was arrested in the downstairs or upstairs apartment. Godbee said, "The suspect was within the scope of our search warrant." He added that the warrant allowed police to search both units.
http://www.detnews.com/article/20100516/METRO/5160325/1409/Police-accidentally-shoot-7-year-old-girl-in-house-search
Police retract the "struggled with" claim:
The police initially claimed Jones was shot after her grandmother had an altercation with one of the officers. They now say the contact with the grandmother was incidental and the gun discharged accidentally.
http://reason.com/blog/2010/05/17/detroit-girl-7-killed-in-swat
The little girl wasn't harboring anybody.
I have never seen any proof the cops knew a killing spree was in progress at Columbine.
I agree the issue is not a simple one. My primary point is that the proper course is always obvious in hindsight. Not so much at the time.