In some ancient civilizations the Wolf was a symbol of the underworld. In Egypt, the guardian of the dead was Anubis who was a wolf-headed god. The jackal portrayed as black was the symbol of both death and regeneration.
William is also the one who hid inside the suits and kidnapped and killed children, leading to the assumption that William Afton is The Purple Guy of FNaF 2 and 3 (he is killed at the end of the book when Charlie sets off the spring locks in his suit).
There, he again met Jessica Jones, who was now working as a private investigator in the employ of a group people whose family members had met their demise while in the control of the Purple Man. Instead of confessing his guilt, Killgrave ridiculed Jones.