The scoping out of the location not just to shoot but also to defend from within.
Some people with military experience describe the set up in the hallway on the 32nd floor as the perfect kill zone.
I have no military experience - but I’m guessing the “perfect kill zone” is not much more than having the second room to flank from, and/or to retreat to. Although if it was me, I would have figured out a way to not have the smaller, flanking room registered to me.
How many did he kill in the perfect kill zone.
It’s called a fatal funnel and is as basic as it gets for tactics. Easily defeated by any SWAT team with flash bangs and smoke/nvg. He setup two cameras to monitor the door, hardly difficult. To be honest you can learn all this playing Rainbow Six or being an avid reader of Tom Clancy etc.
Stephen was a smart guy and it’s really not hard to learn this stuff on your own.
I don’t see any part of his plan that required assistance.