This is not to blame the police but to be able to learn how things unfolded and what was done
right and what was done wrong.  You repeatedly hear that after the Columbine school killings,
police across the nation revised their tactics on how they were going to respond to a mass
shooting and hostage situation. They were no longer going to wait outside and allow the shooter/shooters to kill everyone they could but would respond immediately to take out the shooter.
From what we know thus far, revised time line or what, when police did get to the floor where the
shooter was, they did not attempt to make a dynamic entry as he had the advantage and firepower
to take them on so they waited instead for their SWAT team to arrive.  But by the time the SWAT
team arrived and were ready to go, he had already done his dirty deed and seeing that the gig was
up via his video camera's he elected to kill himself or at least that is what we know or been told.