RCMP Const. Heidi Stevenson, a 23-year veteran of the force, was killed and another officer was injured while pursuing the suspect, Leather told reporters Sunday.

The gunman, identified as Gabriel Wortman, 51, is dead, he said. There was at least one exchange of gunfire between the suspect and police.

RCMP spokesperson Daniel Brien told POLITICO late Sunday that 16 people, not including the suspect, died.

The death toll surpasses the 1989 École Polytechnique massacre in Montreal, where a gunman killed 14 women before killing himself.

"This was a quickly evolving situation and a chaotic scene," said Leather, who described at least part of the assault as "very random in nature."

"He moved across the northern part of the province and committed, it would appear, several homicides."

Prime Minister Justin Trudeau issued a statement Sunday saying he was saddened to hear about the "senseless violence" in the Atlantic province.

"Our hearts go out to the people who have lost loved ones, and to the RCMP family mourning a fallen officer," Trudeau said. "I also hope for a full recovery for the people who were injured, including one RCMP member who is in hospital being treated for non-life-threatening injuries."

Prime Minister Justin Trudeau. | Sean Kilpatrick/The Canadian Press via AP

Leather said police responded to a call late Saturday at a residence in the rural community of Portapique, where they found "several casualties" inside and outside the home.

He said officers tracked the suspect, who wore at least part of a police uniform and drove a vehicle made to look like an RCMP cruiser. Along the way, police discovered structures on fire, Leather said.

Lee Bergerman, assistant commissioner of the Nova Scotia RCMP, told a press conference that it was a devastating day for the province that "will remain etched in the minds of many for years to come."

Public Safety Minister Bill Blair said it was a heartbreaking day for all of Canada. "I know the people of Nova Scotia are especially shaken and looking for answers."