OPP Lay Fourth Charge in High-Profile Ottawa-Region Homicide Case
Ottawa-area residents following the Robbie Thomson homicide case have a new development to digest: Ontario Provincial Police have charged a fourth person in connection with the killing, continuing what has become one of the more complex and closely watched investigations in the region in recent years.
The newest person charged has been identified as Mark Fenton, according to OPP. Fenton joins three others who have previously faced charges tied to Thomson's death — a case that began when Thomson, a man from the Smiths Falls area southwest of Ottawa, went missing in 2023.
What We Know About the Case
Robbie Thomson's disappearance in 2023 set off a prolonged investigation that eventually led OPP to treat the case as a homicide. The Smiths Falls area, a small community roughly 80 kilometres southwest of Ottawa along the Rideau River corridor, became the focal point of the probe.
OPP have been methodical in their approach, laying charges in stages rather than all at once — a pattern that suggests investigators have been building their case carefully and following new leads as they emerge. The fourth arrest signals the investigation remains active and that police believe multiple individuals played a role in Thomson's death.
Details about the specific charges against Fenton, as well as the circumstances of Thomson's killing, have not been fully disclosed by OPP at this stage, which is common in ongoing homicide proceedings to protect the integrity of the case ahead of trial.
A Region Watching Closely
For communities in the Ottawa Valley and the Rideau Lakes region, the Thomson case has been a sobering reminder of violent crime in areas that often feel removed from the pressures of urban centres. Smiths Falls, a town of roughly 9,000 people, has seen significant attention drawn to it through this investigation.
OPP's Eastern Region detachments have handled the case, working alongside forensic and investigative units. The OPP routinely covers rural and small-town Ontario east of Toronto, including the swath of communities between Ottawa and Kingston.
What Comes Next
With four people now facing charges, the case moves further into the court process. Each accused will have their own proceedings, and the full scope of what happened to Robbie Thomson may only become clear once matters reach trial.
OPP have not indicated whether additional arrests are anticipated, though the staged nature of the charges over the past year suggests investigators have continued to gather evidence and identify individuals allegedly involved.
For the Thomson family and those who knew him, each new development brings both a measure of accountability and a continued painful reminder of the loss they've endured.
If you have any information related to this investigation, OPP can be reached at 1-888-310-1122 or through Crime Stoppers anonymously.
Source: CBC Ottawa
