10 Reasons Why Zodiac Killer MAY Have Been Solved

Crucially, Doerr has a history of violence that further posits him as a potential suspect, or in the very least suggests him capable of heinous acts such as murder.

For starters, in a 1974 letter to the editor of his favourite zine, Green Egg, Doerr straight-up implied that he's killed people, and in his own zine Pioneer, stated "the only good enemy is a dead enemy."

Furthermore, Doerr was reportedly discharged from the Military after a year's service for attempting to shove a fork down someone's throat.

And Doerr's daughter Gloria, who will become a more vital piece of the puzzle later on, has corroborated that Doerr was a violent man throughout his life, with a history of abusing her and other family members.

A man being violent doesn't immediately peg him as a serial killer, yet his not-so-cryptic suggestion in writing that he has killed someone certainly raises some major red flags.