It almost seems like the killer has figured this out over time and has settled on this as an MO after trying out some other locations first.
I am amazed that this individual has been able to operate without a witness for so many days. I'm sure he doesn't have much time left. He's going to screw up soon. He has to do everything perfectly from this point on; even a single misstep will result in capture or death.
(steely)
He takes one shot. He has been successfull 80% of the time, but if he is not, he doesn't wait around to find out, or take another shot that might give him away. Just one good shot. That is his objective.
He is so divorced from his actions that he is like a machine. Find an opportunity, get off one shot, make your getaway. Very dispassionate. If he keeps it up, he most certainly will screw up and get caught. But he adheres to his formula despite a massive manhunt. To me, this seems to indicate an experienced professional who can control the rush of adrenilin coursing through his veins.