[clearcarbon]

"The perp could have put himself in position a day or so ahead of time and pulled a ladder up with him so as to not draw suspicion. Or, climbed up a ladder he brought for the purpose and propositioned. Or used one that has already been there."

I'm inclined to believe it was rehearsed. Did the shooter expect to survive?

[Mariner]

“Did the shooter expect to survive? “

It’s nearly certain he was promised evac.