One of the most frustrating questions regarding the death of Teresa Halbach in Netflix’s crime documentary Making A Murderer is “If Steven Avery didn’t kill her, who did?” We’ve heard a couple of theories offered up by internet sleuths and Steven Avery himself, but there’s been nothing very conclusive – partially because the police did such a terrible job of following leads once they’d decided Avery was the killer. But former police sergeant and FBI cold case task force worker John Cameron thinks he knows who did it.

According to Cameron, Edward Wayne Edwards was a serial killer that liked to set other people up for the crimes he committed and was obsessed with the media attention surrounding murder. Sometimes he would pick victims based on reports he read in newspapers. Other times his target would be the person being set up for murder, with the victim being almost inconsequential.

Officially, Edwards has been convicted of five deaths from 1977 to 1996, including the murder of his adopted son for insurance money. But there’s a growing number of people that buy into the theory that he is responsible for some of the biggest unsolved murder cases in American history, including the Zodiac killings, the West Memphis Three, Chandra Levy, and Jon Benet Ramsey. Now Cameron believes Edwards may have something to do with Teresa Halbach’s death as well.

Related: Who Does Steven Avery Think Killed Teresa Halbach?

What ties Edwards to all these cases? Location, letters to press/police/families of victims, and blogs written by Ed Edwards himself. His daughter, who was the one who ended up turning him in to the authorities, has also put forward information linking Edwards to more murders than he was officially tried for.

Here are some things that may make you go hmmm when considering Cameron’s theory that Edwards killed Halbach: