When Jake visits William's house, Jake asks, "You hear what's been happening lately?," and William replies, "You mean the murders?," clearly referring to murders in the plural. William is later surprised to hear that the body count is "up to three now," even though the killer murdered both his second and third victims at the same crime scene.
After the Harvest Killer cuts off the ear of his third victim, the ear is still visibly attached in a later scene.