As soon as it started, he would have gone outside, been fired upon and went back into the commons and engaged then from there.
He would have also helped in the evacuation of students from the commos, as well as held his position at the stairs guarding the library hallway.
This would have probably forced them away from the library and the would have gone to the north side of the school around the art wing.
They porbably wouldn't have tried to go to the commons, if they were forced away multiple times.
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Falling out of airplanes and hiding out in holes
Waiting for the sunset to come, people going home
Jump out from behind them and shoot them in the head
Now everybody dancing, the dance of the dead
The dance of the dead, the dance of the dead