People in Saskatchewan have received a grim introduction to the White Boy Posse — the Alberta criminal gang connected to the men charged with murdering a Saskatoon mother of four.

On Tuesday, Saskatoon police announced that the three Alberta men — Joshua Petrin, Randy James Wayne O'Hagan, and Kyle Darren Halbauer — have been charged with first-degree murder in the death of Lorry Ann Santos, who was 34 when she went to the door of her home the morning of Sept. 12, 2012 and was shot to death.

Randy James Wayne O'Hagan has been charged with first-degree murder in the deaths of Lorry Ann Santos, Bryan Gower and Robert John Roth Sr. (Facebook)

According to police, the three men were members of White Boy Posse, a gang known for its racist ideology, cocaine dealing and violence.

When Edmonton police announced a major bust involving the gang in 2009, one of the seized items they displayed was a Nazi flag.

"They're not posing, they're very, very serious about white supremacy," said Mark Totten, an Ottawa author and gang specialist.

'They're not posing, they're very, very serious about white supremacy'—Mark Totten

"But they're also very serious about making money."

In 2008, police jailed a number of the Posse leadership which hurt, but apparently didn't kill, the gang.

Police say gang members killed Lorry Santos in September by mistake while trying to break into the Saskatoon drug market; they had the wrong address.

Two other killings in Alberta

Police also believe members of the gang killed a man outside Lloydminster two weeks later, and then decapitated another man, whose head was found in Edmonton. Charges in those Alberta homicides were also announced Tuesday.

Kyle Darren Halbauer is charged with first-degree murder in the deaths of Lorry Ann Santos and Bryan Gower. (Facebook)

Halbauer and O'Hagan are charged with the death of Bryan Gower, 35, while O'Hagan and a fourth man, Nikolas Jon Nowytzkyj, 32, of Wainwright, Alta., have been charged with the murder of Robert John Roth Sr. of Lloydminster.

Roth's partial remains were found near Ranfurly, Alta., while his severed head was discovered in Edmonton five days later.

'They're incredibly violent'—Mark Totten

Totten says the public should be worried about the White Boy Posse.

"They are white supremacists, they have had ties with the Hells Angels over the past number of years and they're incredibly violent," he said.

The announcements about the arrests came out the same day Statistics Canada released its annual report on homicides in Canada.

It showed that gang-related homicides are increasingly becoming a concern in Saskatchewan, particularly in Saskatoon.

Last year, there were nine gang-related homicides in Saskatchewan, the report said.