User blog comment:The Milkman/Indoctrination Theorists Say the Darndest Things, Part II/@comment-5830255-20121205082807/@comment-1440333-20121205152619

Yet Manuel appears in Firewalker and is not indoctrinated. Hell for all we know the sound they heard could have been the Reaper sounds we all  hear in-game. Maybe those noises are always telepathic.