March 3, 2005 Mayerthorpe RCMP Officers Killed

On March 3, 2005, you'd witness the deadliest single day for Canada's RCMP in modern history. Four young constables — Anthony Gordon, Leo Johnston, Brock Myrol, and Peter Schiemann — arrived at James Roszko's farm near Mayerthorpe, Alberta to execute a search warrant tied to stolen property and a suspected marijuana operation. Roszko ambushed them inside a Quonset building with a semi-automatic rifle, killing all four before turning the weapon on himself. There's much more to this devastating story.

Key Takeaways

• On March 3, 2005, four RCMP officers were killed at James Roszko's farm near Mayerthorpe, Alberta, marking Canada's deadliest single day for the RCMP.
• The four fallen officers were Constables Anthony Gordon, Leo Johnston, Brock Myrol, and Peter Schiemann, aged between 25 and 32.
• James Roszko ambushed the officers inside a Quonset building using a semi-automatic rifle before turning the weapon on himself.
• Officers were initially on the property executing a search warrant related to stolen property and a suspected marijuana-growing operation.
• Two accomplices, Shawn Hennessey and Dennis Cheeseman, helped Roszko return to the property and later pleaded guilty to manslaughter.

What Led RCMP to Roszko's Farm That Day?

On March 3, 2005, RCMP officers arrived at James Roszko's farm near Mayerthorpe, Alberta, to execute a search warrant tied to stolen property and a suspected marijuana-growing operation on the premises.

The warrant procedure followed standard investigative steps after authorities linked the property to both property theft and illegal drug activity. You can think of that day as routine, at least on paper. Officers had legitimate legal grounds to be there and followed proper channels before entering.

What they didn't know was that Roszko had returned to the farm and was waiting inside a Quonset building. What started as a lawful operation to address criminal activity on the property quickly became the deadliest single day for the RCMP in modern Canadian history.

Inside the Quonset: How the Mayerthorpe Ambush Unfolded

What the officers found when they entered the Quonset building on Roszko's property that morning wasn't an empty structure. The Quonset layout offered concealment, and Roszko used it to his full advantage. Despite the entry tactics the officers employed, they couldn't anticipate what was waiting inside.

James Roszko had positioned himself and opened fire with a semi-automatic rifle before the officers could react. The Fatality Inquiry later confirmed that all four constables — Anthony Gordon, Leo Johnston, Brock Myrol, and Peter Schiemann — died almost instantly. It wasn't a confrontation. It was a cold-blooded ambush.

After killing all four officers, Roszko turned the weapon on himself. What unfolded inside that building in minutes would become the worst single-day officer loss in modern Canadian history.

The Fallen Four: The Officers Killed at Mayerthorpe

Four names became synonymous with sacrifice the moment the gunfire inside that Quonset building fell silent: Constable Anthony Gordon, 28; Constable Leo Johnston, 32; Constable Brock Myrol, 29; and Constable Peter Schiemann, 25. You'll find their legacy honored at Fallen Four Memorial Park in Mayerthorpe, where bronze sculptures of each officer stand facing four directions.

The Fatality Inquiry confirmed all four died almost instantly, leaving behind colleagues, families, and a nation in shock. Their deaths shattered the sense of police camaraderie that holds officers together through dangerous work, reminding you that no call is ever routine. Much like the rapid mobilization achieved through expanded military training camps, the RCMP's response to Mayerthorpe prompted a nationwide reassessment of officer safety protocols and training standards.

Yet from that grief, community healing slowly took root. Mayerthorpe carried their memory forward, refusing to let the tragedy define the town without also defining its resilience.

Who Was James Roszko?

Behind the violence of March 3, 2005, stood a man with a long and troubling history: James Roszko, the property owner who ambushed and killed all four officers inside his Quonset building before turning the weapon on himself.

His own father reportedly described him as a "wicked devil," offering a glimpse into a deeply fractured family background.

Roszko had accumulated a lengthy criminal record and was linked to stolen property and an illegal marijuana-growing operation on his farm.

Those close to the case noted serious concerns about his mental health over the years.

Two men, Shawn Hennessey and Dennis Cheeseman, later pleaded guilty to manslaughter for helping Roszko return to the property, making it clear the ambush wasn't carried out entirely alone.

How Did James Roszko Get Back to the Farm?

One of the most chilling details to emerge from the investigation was how Roszko managed to slip back onto his own property while officers were still there. Roszko hadn't relied on luck or obvious escape routes — he'd gotten help. Two men, Shawn Hennessey and Dennis Cheeseman, assisted him in returning to the farm undetected while RCMP were conducting their search.

That assistance proved fatal for four officers. When investigators pieced together what happened, Hennessey and Cheeseman couldn't avoid the legal consequences of their role. Both men pleaded guilty to manslaughter, acknowledging that they'd helped Roszko get back to the property knowing he was armed and dangerous.

Their involvement transformed what might've seemed like a straightforward search operation into a calculated, deadly ambush.

Hennessey and Cheeseman: The Men Who Helped Roszko

Shawn Hennessey and Dennis Cheeseman weren't strangers to Roszko — they knew exactly who they were helping and what he was capable of. Yet they helped him return to the farm anyway, and that decision carried enormous legal culpability. Both men later pleaded guilty to manslaughter, acknowledging their role in enabling the ambush that killed four officers.

You can imagine how their actions shook Mayerthorpe beyond the immediate tragedy. The community impacts ran deep — neighbors had to reckon with the fact that people from within their own circles had facilitated one of Canada's deadliest law enforcement attacks. Trust fractured. Grief intensified. The plea agreements confirmed what many feared: the killings weren't just Roszko's doing alone. Others had made deliberate choices that sealed the fate of four young constables.

A Nation in Mourning: How Canada Reacted to Mayerthorpe

When news of the Mayerthorpe tragedy broke on March 3, 2005, it hit Canada like a gut punch. You couldn't turn on the television or open a newspaper without feeling the weight of national grief settling in. The media response was immediate and intense — outlets across the country covered the story with a depth rarely seen for a single policing event.

Canadians mourned four young officers — Anthony Gordon, Leo Johnston, Brock Myrol, and Peter Schiemann — who'd walked into a Quonset building and never walked out. Communities held vigils. Politicians offered condemnations. The RCMP buried its own with full honors. You sensed that something had fundamentally shifted in how Canadians understood the dangers their officers faced every single day.

Why Was Mayerthorpe the Worst RCMP Loss in Decades?

To understand why Mayerthorpe hit so hard historically, you have to look at the numbers. Before March 3, 2005, the RCMP's worst single-day loss dated back to 1958, when five officers drowned. That's nearly five decades without anything comparable. Then, in one morning, four constables died in a cold-blooded ambush inside a Quonset building on a rural Alberta farm.

The police community hadn't faced a loss like this in a generation. Historians noted that not since 1885 had so many officers fallen in a single Canadian incident. The scale wasn't just shocking — it was historic.

Beyond the statistics, the event forced a reckoning with officer mental health, as survivors, colleagues, and entire departments struggled to process grief on a national scale.

Fallen Four Memorial Park in Mayerthorpe

Grief on that scale doesn't disappear — it finds a place to live. In Mayerthorpe, it lives at Fallen Four Memorial Park, where four bronze sculptures of Anthony Gordon, Leo Johnston, Brock Myrol, and Peter Schiemann stand facing four separate directions. That memorial design carries quiet intention — each officer facing outward, still on watch.

When you visit, you're standing where a community chose to anchor its loss in something permanent. The park serves as more than a landmark; it's where community ceremonies bring people together each year to mark what happened on March 3, 2005. Those gatherings remind you that the tragedy didn't end with the headlines. It shaped Mayerthorpe's identity, and the memorial guarantees the Fallen Four remain present — not just remembered, but honored.