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)The parents of four dead Mounties looked on as medical examiner Dr. Bernard Bannach testified Monday at the start of a long-awaited inquiry into the RCMP constables' slayings near Mayerthorpe, Alta., almost six years ago.

In Stony Plain provincial court, Bannach detailed the findings of five autopsies — those of the officers and gunman James Roszko.

RCMP constables Anthony Gordon, Leo Johnston, Brock Myrol and Peter Schiemann were killed during a criminal investigation on Roszko's property 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.

Johnston was shot four times, Schiemann three times and Myrol and Gordon twice each. All the gunshot wounds were the result of fire from a rifle, said Bannach.

Roszko died with three gunshot wounds — one wound to his chest was self-inflicted while the two others were likely from pistol fire, he said.

The parents of the Mounties have been granted the opportunity to ask questions throughout the inquiry.

Grace Johnston, mother of slain constable Leo Johnston and Doreen Jewell-Duffy, mother of Anthony Gordon, embrace outside of the Stony Plain courthouse Monday morning. (CBC)Johnston's mother, Grace Johnston, fought through tears to ask if Bannach could determine which shot hit her son first. Bannach said he could not.

Johnston then asked how long it would have taken her son to die. Bannach said 10 to 15 seconds, as one of the bullets hit Leo Johnston's spine and heart.

"If there is any comfort in what we heard today it's that Leo and the other three of his colleagues did not suffer," Johnston told reporters afterwards. "They died in what is to be considered instantly."

Following a break, one of the bailiffs who tried repossessing Roszko's truck the day before the massacre took the stand.

Mark Hnatiw recalled teasing Myrol who was on the job just two weeks out of training.

"I teased him about his shiny new boots," he said. "He took it quite well."

Hnatiw said he overheard police officers talking about how violent and dangerous Roszko was.

He described the officers as being keen, alert and professional and began weeping on the stand when he described hearing the news the next day about the ambush.

"I thought I had put it to rest but it brings back some feelings and just what a travesty it was and what a waste of life," Hnatiw told reporters outside the courthouse.

The events of that day led him to change careers, Hnatiw said.

The inquiry is scheduled to run until Feb. 1.

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.

With files from John Archer and Briar Stewart