((ST Note: I am assuming Jack is still planning to take a shot from the roof of the building across the street.
That building is modern twelve-story office building. Climate-controlled, the windows do not open. It contains many businesses, some of them open 24/7 as far as Jack has been able to determine, and there is some degree of traffic all through the night. Some of the floors are taken up by a single business, and some of the floors are much more active at night than others. There is a security desk in the lobby, manned by two security guards. There are two elevators and two stairwells. During an earlier visit, Jack was able to discover that one of them provides roof access, but the door to the roof is a very sturdy metal door, and locked.
There are cameras in the lobby, the elevators and the hallways, but as far as Jack has seen, the guards spend more time eating delivery pizza and reading newspapers and sports magazines than they do watching the monitors. Every half hour or so, one of the guards gets up and patrols the building. The guards wear belts upon which they carry key rings, radios, pepper spray, shock-resistant plastic tonfa-style batons and holstered pistols. ))