Isaac, sitting in the passenger’s seat, glanced down at his watch. 4:23.

Abraham steered the black Toyota 4Runner out of the street and into the parking lot on the south side of the Western Mills Mall in the suburbs of Denver, Colorado, and casually up and down a couple of aisles. To anybody on the outside, it would appear as if he was looking for a prime parking spot on the second Sunday of the Christmas shopping season.

What he was really doing was surveilling the parking lot to make sure that the police presence was no more than they expected it to be.

The Western Mills Mall was a behemoth of a shopping structure, covering over a million square feet. From overhead, the mall looks like a gigantic toy train locomotive, with a very long center body, widening out on the east end like the cab of the locomotive. Inside, the layout is essentially a giant rounded, triangular loop in roughly the same shape as Pocono Raceway in Pennsylvania. The main corridor, all 15 feet of width, goes from the east end, where it begins at the theater (which widens into the “cab” structure), and proceeds in a straight line down the length of the mall, past one anchor store on the right, past the food court on the left, past another anchor store on the left and down to the western end. At that point, the corridor angles to the left, then takes a sharp left at another anchor store to head back all the way to the eastern end of the mall where it ends again at the movie theater, passing the food court again on the left.

Isaac found the layout of the mall amusing—suburban housewives and the elderly used it as an indoor race track during the week, getting their exercise by walking the circuit. The only place in the mall where you could cut across from one side to the other was through the food court, which is where the mall walkers went to eat off their exercise. They had no way of knowing that very food court was about to become a graveyard.