The San Francisco Chronicle article on April 20th 1970 only described the drawing on Robert Salem's apartment wall as "a weird cross like design with an arc, similar to the Zodiac's circled cross insignia". There was no mention of an Egyptian ankh or Crux Ansata, no mention of a crucifix style design - and other than the writing "Satan Saves Zodiac" - no mention of Christianity or Jesus Christ. The ankh or key of life (drawn in blood on the apartment wall of Robert Salem) is an ancient Egyptian hieroglyphic symbol used in Egyptian art and writing to represent the word for "life" and, by extension, as a symbol of life itself. It was especially commonly held in the hands of ancient Egyptian deities, or being given by them to the pharaoh, to represent their power to sustain life and to revive human souls in the afterlife. Because it symbolizes immortality and the universe it was initially borrowed by the fourth-century Coptic Christians who used it as a symbol to reinforce Christ's message that there is life after death. The ankh cross as a symbol of eternal life eventually lost its loop at the top to become the Christian cross which, like the ancient ankh, is worn by believers in Jesus Christ in the present day for the same reason: to identify with their god and all that god promises. link. Much more recently, the ankh has become a popular symbol in modern Western culture, particularly as a design for jewelry and tattoos. Its resurgence began when the counterculture of the 1960s stirred a greater interest in ancient religions.
Despite no direct mention of Christianity, Jesus Christ or the Egyptian Ankh in the San Francisco Chronicle article on April 20th 1970, the Zodiac Killer within hours would manufacture a code letter containing the three circled eights (which represents the name Jesus in Christian numerology, with the number 8 representing rebirth and regeneration, and infinity/eternity), along with a Christian anchor symbol. Christians adopted the anchor as a symbol of hope in future existence because the anchor was regarded in ancient times as a symbol of safety. For Christians, Christ is the unfailing hope of all who believe in him: Saint Peter, Saint Paul, and several of the early Church Fathers speak in this sense. link.