Const. Anthony Gordon, top left, Const. Lionide (Leo) Johnston, top right, Const. Brock Myrol, bottom left, and Const. Peter Schiemann were killed at Mayerthorpe, Alta., in 2005. (CBC)A public inquiry will begin Monday morning into the shooting deaths of four Mounties who died more than five years ago on a northern Alberta farm.

RCMP constables Anthony Gordon, Leo Johnston, Brock Myrol and Peter Schiemann were killed while assisting with a criminal investigation on the property of James Roszko near Mayerthorpe, Alta.

On March 3, 2005, Roszko gunned down the four officers guarding a Quonset hut on his property. It had been cordoned off the day before as part of an investigation into possible vehicle theft, during which police had also found marijuana plants.

Roszko, who had spent several years in prison on 12 prior criminal convictions, including sexually assaulting a boy, then turned his gun on himself.

In July 2007, the RCMP announced it had arrested two brothers-in-law from Barrhead, Alta. — Dennis Keegan Rodney Cheeseman, 23, and Shawn William Hennessey, 28 — and each was charged with four counts of first-degree murder.

The force accused the men of aiding and abetting Roszko, and therefore being parties to the homicides.

In January 2009, both men pleaded guilty to lesser charges of manslaughter. Cheeseman was sentenced to 12 years in prison, while Hennessey received 15 years.

The inquiry, which could not begin until all criminal proceedings related to the case had wrapped up, will begin at 9:30 a.m. MT in provincial court in Stony Plain with presiding assistant Chief Judge D.R. Pahl.

Testimony will come from former and current RCMP employees, including Senior Deputy Commissioner Rod Knecht, who was the Criminal Operations Officer of "K" Division RCMP at the time of the shootings.

In Alberta, public inquiries held under the Alberta Fatality Inquiries Act are limited to establishing the cause, manner, time, place and circumstances of death, as well as the identity of the deceased, police said.

The judge may make recommendations on the prevention of similar occurrences but is prohibited, under the act, from making findings of legal responsibility.