Mayerthorpe tragedy

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.