Case file
Mayerthorpe tragedy
Documents violence · suicide — written to inform, not to shock.
On March 3, 2005, four Royal Canadian Mounted Police constables — Anthony Gordon, Lionide "Leo" Johnston, Brock Myrol, and Peter Schiemann — were shot and killed on a farm owned by James Roszko near Rochfort Bridge, north of Mayerthorpe, Alberta. Roszko then died of a self-inflicted gunshot wound. The killings occurred while officers were on the property executing a search warrant related to a suspected stolen-vehicle chop shop and a marijuana-growing operation.
The events began on March 2, 2005, when civil bailiffs attempted to repossess a truck from Roszko, who had a criminal record including violent and sexual offences and was subject to a firearms prohibition. After Roszko fled, RCMP officers who responded found evidence of a chop shop and grow-op, and a warrant was obtained. Overnight, officers searched and seized marijuana plants and equipment; two constables, Gordon and Johnston, remained overnight for scene security. Roszko contacted Shawn Hennessey and Dennis Cheeseman, who assisted him in returning near his farm and provided him with a rifle. On the morning of March 3, as four constables entered the quonset building on the property, Roszko — who had concealed himself inside — opened fire, killing all four almost instantly. He then exchanged fire with a fifth officer, Constable Stephen Vigor, who wounded him, before Roszko retreated into the quonset and fatally shot himself.
An extensive two-year RCMP investigation followed, involving forensic searches of the property, cell phone record analysis, and an undercover "Mr. Big" operation. On July 9, 2007, Hennessey and Cheeseman were charged as parties to the offences, a charge that under Canadian law can amount to first-degree murder when a police officer is killed in the line of duty. In June 2008 they were committed to stand trial after a preliminary inquiry. On January 19, 2009, both men pleaded guilty instead to four counts of manslaughter. On January 30, 2009, the Court of Queen's Bench sentenced Hennessey to 10 years and 4½ months, and Cheeseman to 7 years and 2½ months, after credit for guilty pleas and time served. Both men's appeals to the Alberta Court of Appeal were dismissed in 2010, and the Supreme Court of Canada denied leave to appeal in August 2011. Cheeseman was released in 2013 and Hennessey was paroled in 2015.
An Alberta Fatalities Inquiry, convened under the Fatality Inquiries Act, began in January 2011 and concluded that the four officers' deaths were homicides and Roszko's death was a suicide, issuing recommendations including improved firearms for RCMP officers, which contributed to the later adoption of the C8 rifle. Memorials to the four officers, known as the "Fallen Four," were established in Mayerthorpe and Whitecourt, and a national memorial service was held in Edmonton in March 2005, attended by Prime Minister Paul Martin, Governor General Adrienne Clarkson, and nearly 10,000 police officers.
Key facts
- Victims
- Peter Schiemann, Anthony Gordon, Brock Myrol, Lionide "Leo" Johnston
- Date
- 2005
- Location
- James Roszko's farm near Rochfort Bridge, north of Mayerthorpe, Alberta
- Case status
- solved
Case timeline
2005-03-02
Civil bailiffs attempt to repossess a truck from James Roszko; RCMP officers respond and discover evidence of a stolen-vehicle chop shop and marijuana grow operation.
2005-03-03
James Roszko shoots and kills Constables Anthony Gordon, Leo Johnston, Brock Myrol, and Peter Schiemann inside a quonset building on his farm, then fatally shoots himself after an exchange of gunfire with Constable Stephen Vigor.
2005-03-10
A national memorial service for the four slain officers is held in Edmonton.
2005-05-19
Queen Elizabeth II attends a ceremony honouring the slain officers at RCMP Academy, Depot Division in Regina.
2007-07-09
Shawn Hennessey and Dennis Cheeseman are charged as parties to the offences committed by Roszko.
2008-06
Hennessey and Cheeseman are committed to stand trial on murder charges following a preliminary inquiry.
2008-07-04
The Fallen Four Memorial Park opens in Mayerthorpe.
2009-01-19
Hennessey and Cheeseman plead guilty to four counts of manslaughter.
2009-01-30
The Court of Queen's Bench sentences Hennessey to 10 years and 4½ months, and Cheeseman to 7 years and 2½ months.
2010-09-27
The Alberta Court of Appeal dismisses Hennessey's appeal and, by majority, dismisses Cheeseman's appeal.
2011-01-11
The Alberta Fatalities Inquiry into the deaths begins in Stony Plain Provincial Court.
2011-08-25
The Supreme Court of Canada dismisses both men's applications for leave to appeal.
2011-10-21
RCMP Commissioner William J. S. Elliott announces the adoption of the C8 Rifle following recommendations from the Fatalities Inquiry.
2013
Dennis Cheeseman is granted statutory release.
2015
Shawn Hennessey is paroled.
Best coverage
No approved coverage links are attached yet.
People
James Roszko
CONVICTEDPerpetrator of the shootings; died by suicide at the scene, and the Fatalities Inquiry concluded the officers' deaths were homicides committed by him.
citation on file
Dennis Cheeseman
CONVICTEDPleaded guilty on January 19, 2009 to four counts of manslaughter for assisting Roszko's return to the farm; sentenced to 7 years and 2½ months.
citation on file
Peter Schiemann
VICTIMRCMP constable killed in the March 3, 2005 shooting.
citation on file
Anthony Gordon
VICTIMRCMP constable killed in the March 3, 2005 shooting.
citation on file
Brock Myrol
VICTIMRCMP constable killed in the March 3, 2005 shooting.
citation on file
Lionide "Leo" Johnston
VICTIMRCMP constable killed in the March 3, 2005 shooting.
citation on file
Shawn Hennessey
CONVICTEDPleaded guilty on January 19, 2009 to four counts of manslaughter for assisting Roszko's return to the farm; sentenced to 10 years and 4½ months.
citation on file
Stephen Vigor
LAW ENFORCEMENTRCMP Auto Theft investigation constable who exchanged gunfire with Roszko outside the quonset.
citation on file
Places
Common questions
- What happened to the victim?
- On March 3, 2005, James Roszko shot and killed four RCMP constables at his farm near Mayerthorpe, Alberta, before killing himself; two men who helped him return to the property later pleaded guilty to manslaughter.
- Where did the crime happen?
- James Roszko's farm near Rochfort Bridge, north of Mayerthorpe, Alberta.
- Who was convicted?
- James Roszko (Perpetrator of the shootings; died by suicide at the scene, and the Fatalities Inquiry concluded the officers' deaths were homicides committed by him.), Dennis Cheeseman (Pleaded guilty on January 19, 2009 to four counts of manslaughter for assisting Roszko's return to the farm; sentenced to 7 years and 2½ months.), and Shawn Hennessey (Pleaded guilty on January 19, 2009 to four counts of manslaughter for assisting Roszko's return to the farm; sentenced to 10 years and 4½ months.).
- What is the current status of the case?
- Status: solved.
Sources
- Mayerthorpe tragedywikipedia · Wikipedia · 2026-07-07
- Contemporaneous coverage — CBC Newsnews · CBC News · 2026-07-07
- Contemporaneous coverage — The Globe and Mailnews · The Globe and Mail · 2026-07-07
