Lin Wu stealthily explored, circling the rooftop for more than half a revolution and only discovered 35 soldier zombies. They weren't scattered but were congregating within a 10-meter radius of the helicopter, either moving or remaining stationary.
Lin Wu squatted 20 meters away from the helicopter and watched carefully for a long time yet noticed a problem. Then he moved to the passageway, which was empty, and both elevator doors were closed tight. Looking down from the stairwell, he saw no zombies. As Lin Wu turned to head back to the rooftop, he spotted something amiss, a puddle of water by the elevator. It was as if someone had stopped by the elevator entrance after walking in from the rain, droplets continuously falling.
Lin Wu pulled out Silent Night and fired a shot in the direction of the droplets, creating a hole immediately. Without hesitation, he performed a Lock Head shot, and a corpse fell to the ground.