The man suspected of killing his girlfriend, her father and himself in Halifax at the beginning of the year had a lengthy criminal record in Ontario, including a history of firearm offences, Global News has learned.
Court documents from a sentencing in Toronto a decade ago detail Matthew Costain’s criminal record that began at the age of 14, arrests involving illegal guns and a history of issues with drugs.
In 2014, despite being a “repeat offender,” an Ontario judge said he believed Costain was ready to change and said there were “strong prospects for rehabilitation in this case.”
Five years later, Toronto police issued an arrest warrant for Costain relating to a 2019 nightclub shooting in the city that injured five people.
And then, as the new year dawned, Halifax Regional Police said they believed 39-year-old Costain had shot Cora-Lee Smith, 40, and her 73-year-old father, Bradford Downey, before dying of a self-inflicted gunshot wound.
Police said Costain had been in a relationship with Smith and said they believed the fatal incident was a case of intimate partner violence.
First offence at 14
An Ontario Superior Court of Justice ruling handed down in Toronto on May 29, 2014, said Costain’s first criminal activity was recorded at the age of 14 in 1999 when he was involved in an armed robbery.
Two years later, he faced a mischief charge, along with other charges that included assaulting a police officer. In 2006, at the age of 21, he was convicted of armed robbery, possession of a loaded prohibited firearm and possession of a firearm.
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He then went six years without a court appearance, according to the documents, before he was arrested in 2012 on drug and firearm charges and sentenced in 2014.
During his early years, the court documents show Costain struggled with drug addiction, and education, becoming a father at just 14 years old. By the time he was sentenced in 2014, Costain had three children and was engaged in a “supportive,” five-year relationship with the mother of his second and third children.
Costain himself was one of five children and, according to the 2014 ruling, had “good family support.”
He didn’t finish his high school education and moved around often, which he said was difficult. Costain dropped out of high school because he was using drugs and was struggling at home. The 2014 ruling said his father was an abusive alcoholic and his mother was often in hospital.
According to the ruling, Costain had “recognized and acknowledged that he has a serious drug problem” and, during his pretrial custody, he had taken part in a drug awareness and support program.
At the peak of his addiction, the ruling said, he took a gram of crack cocaine per day.
Judge hopeful of rehabilitation
Despite a series of offences and court appearances, Justice Michael Quigley said in 2014 he was optimistic that “this repeat offender” was ready to choose a new path and would not re-offend.
“There are said to be strong prospects for rehabilitation in this case,” the decision said.
“The offender himself spoke to me directly, sincerely and thoughtfully, about (i) the position that he finds himself at in his life, (ii) about what he has learned about himself during his lengthy pre-sentence custody, (iii) about some of the strong influences that have come to bear in his life since the commission of these offences, and (iv) of his determination to reform the direction of his future.”
Justice Quigley focused particularly on the death of Costain’s mother and father while he was in pretrial custody as things that weighed on him. Both died in 2013 and Costain was denied permission to attend their funerals.
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“Mr. Costain’s time in custody leading up to this trial has been particularly difficult for him, and arguably profoundly influential of his professed desire to change directions going forward,” the ruling said.
Ultimately, in 2014, the judge imposed what he described as “the most lenient sentence our law will permit me to,” making a plea to Costain to honour his plans to change.
“In imposing this sentence on you today, I also am subject to the same law you are,” he said.
“I hope you will succeed in fulfilling the wishes you expressed to me during the sentencing hearing. So please stay on the right side of the law in future. Make your family proud of you.”
Toronto and Halifax
Five years after he was sentenced in Toronto, however, Costain’s name was again being circulated by law enforcement in relation to a nightclub shooting.
Toronto police issued a warrant for his arrest after a shooting on Aug. 5, 2019, where four people were injured in a gunfight. The warrant was still active at the beginning of 2025, meaning officers never found Costain, nor were the charges he was wanted on ever proven in court.
Then, on Dec. 30, 2024, Halifax Regional Police were called after two people were found inside a vehicle, one dead and the other unresponsive. Officers learned their suspect was nearby at the Halifax Commons, and found him there at 1:30 a.m. New Year’s Day.
The man, later identified as Costain, was found deceased. Police said it’s believed he died by self-inflicted gunshot.
— with files from Global News’ Rebecca Lau