Randy James Wayne O'Hagan, 22, of Lloydminster is charged in the death of Robert John Roth Sr., 54, whose partial remains were found near Ranfurly, Alta., on Oct. 20.
Roth's severed head was found five days later by a passerby in Edmonton.
Nikolas Jon Nowytzkyj, 32, of Wainwright, Alta., also faces a charge of first-degree murder in Roth's death.
O'Hagan and Nowytzkyj are also charged with offering an indignity to a human body.
Roth’s family were shocked by the killing, saying Roth was a quiet man who worked as a manual labourer in the Lloydminster area after previously driving a truck, but police say he had connections to his killers.
O'Hagan, along with Kyle Darren Halbauer, 22, is also charged in the death of Bryan Gower, 35, whose body was found on a rural road near Kitscoty, Alta., on Sept. 25.
Both face charges in the attempted murder of a second man in the same incident.
Killers went to the wrong address
The pair are also charged with first-degree murder in the death of Lorry Santos, 35, who was shot and killed after she answered the door of her Saskatoon home to strangers on Sept. 12.
Police said the killers had gone to the wrong address and Santos was an innocent victim.
An Edmonton man, Joshua Petrin, 29, was also charged with first-degree murder in the shooting.
Police said all four men are members of the White Boy Posse, a drug gang based in northern Alberta with tentacles extending into Saskatoon and the Northwest Territories.
"What is surprising to me and to my teammates is the level of violence they've escalated to certainly in the recent years," said Supt. Ted Miles of the Alberta Law Enforcement Response Team.
"Whether (the arrests) will impact their operations ... we're continuing to investigate," he said.
All four suspects are in custody.
Killings meant to be visible: expert
Author Michael Chettleburgh, who has written two books on Canadian street gangs, says if the killings were done by gang members, it may have been people looking to advance in the organization.
"The shooters tend to be those that are trying to prove something. And trying to work their way up that pyramid. To be recognized as violent. To be recognized as fearless," he said.
Chettleburgh said the White Boy Posse is based somewhere in Alberta and that they are suspected of being a "puppet gang" of the Hell's Angels, dealing drugs for the larger gang.
He said the public nature of the killings may be an attempt to establish a name for the gang.
"The fact that these crimes are very visible to me simply says to me they were designed to be visible. Designed to tell others we're here, we're alive and don't mess with us," he said.