A Canadian denturist who murdered at least 19 people during a 12-hour rampage in Nova Scotia over the weekend killed his ex and her new boyfriend first and then later executed a married couple in front of their children, according to authorities and local media reports.

Gabriel Wortman, a 51-year-old with a life-long obsession with law enforcement, killed “at least 19” people across 55 miles before dying in a Sunday night shootout with police, the Royal Canadian Mounted Police said. The slayings, which Wortman carried out in a police uniform and with two decommissioned RCMP cruisers, occurred at over a dozen crime scenes.

Authorities believe the death toll will continue to rise, as Wortman also burned several homes during his murder spree.

“His ability to move around was certainly aided by the fact he had what looked like a police vehicle and that he was wearing a police uniform,” Royal Canadian Mounted Police Chief Superintendent Chris Leather said in a Monday press conference. The attack is considered the largest mass shooting in Canadian history.

While Wortman’s motive remains under investigation, Leather confirmed that he knew some of his victims and specifically “targeted” them, while others were killed at random.

“We have identified all the crime scenes, however, we’ve been unable to fully examine the crime scenes because, for instance, we have had five structure fires, most of those being residences, and we believe there may be victims still within the remains of those homes,” Leather said.

The murder spree began at 10:30 a.m. on Saturday in rural Portapique, about 60 miles outside of Halifax, where Wortman has a property. One police source told The Toronto Sun, that Wortman initially targeted his 51-year-old “ex (wife or girlfriend)” and her new boyfriend before he began attacking people at random across the province.

Dressed in the RCMP uniform and driving what authorities have described as a police cruiser he refurbished, Wortman was able to pull over his victims or enter their houses before shooting them. At one point, he killed “a mom and dad in front of their children,” the police source said.

“The guy went on a rampage (Saturday night)—burning houses and shooting people,” a police source told the Sun, stating that Wortman’s victims “would have trusted him.” “He got into his police car he had made at home and drove around pulling people over and executing them.”

Police finally cornered Wortman at the Irving gas station and Big Stop restaurant in Enfield—about an hour away from the first murder.

So far, authorities have identified a teacher, a mother of two, an RCMP officer, and several health-care workers as among his victims. Leather said Monday that authorities have not released all of the names of the dead because they have not been able to reach family members or get final confirmation from the medical examiner’s office.

Authorities said Heidi Stevenson, the RCMP officer who was among Wortman’s victims, heroically drove her police cruiser into the 51-year-old’s car in an effort to stop him—before he fatally shot her and stole her vehicle. At least one other RCMP officer, Constable Chad Morrison, was also shot during the incident but is currently home and recovering from his injuries, Leather said Monday.

The Nova Scotia Teachers Union issued a statement Sunday identifying Lisa McCully, an elementary school teacher and mother “with a heart of gold,” as another victim.

Heather O’Brien, a nurse who had worked with the Victorian Order of Nurses for Canada for 17 years, also died in the rampage, her daughter wrote in a Facebook post. The Victorian Order of Nurses also identified Kristen Beaton, “a young wife and mother” who worked as a continuing care assistant, as one of Wortman’s victims.

“I want everyone to remember how kind she was. How much she loved being a nurse,” O’Brien’s daughter, Darcy Dobson, wrote on Facebook. “Let those things define her. Not the horrible way she died.”