Columbine was a bit different in that you had mulitple shooters and a whole shcool building involved. Students were hiding and waiting to be rescued. Giving the gunmen time only meant that you were giving them time to find more victims.
If a gunman has everyone lined up in room and can kill them instantly then it is best not to anger him or set him off because there is no counter assault that can be effective against him. Since I don't seem to be sure of all of the details in this case then I won't make anymore judgements about it at this time. I am just pointing out that force is not always the way to deal with a disturbed person.
Since it seems you missed the first press conference from the State Police, they plan on having another one around 6 with updates.
The policeman made it a point to say that he would not speculate on things he did not know.