Ottawa (CNN) The man behind a deadly Nova Scotia rampage , which began in the quiet town of Portapique on Cobequid Bay, disguised himself as a police officer as he led authorities on a miles-long manhunt across the Canadian province.

The shooter, who at one point was driving a vehicle resembling a police cruiser, is believed to have pulled over random motorists before killing them, a law enforcement official familiar with the investigation told CNN.

When the manhunt ended about 12 hours later, the 51-year-old gunman had killed 18 people, including a police constable, a corrections officer, a nurse and a teacher.

Another police officer was injured, police said, and in Shubenacadie, there were reports of gunshots and torched police vehicles, according to one of CNN's media partners.

The gunman, identified as Gabriel Wortman, left a trail of 16 crime scenes that authorities are still working to process, officials say. The death toll may rise, police said.

"We're 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 which burnt to the ground," said Chris Leather, a Royal Canadian Mounted Police chief superintendent and criminal operations officer in Nova Scotia.

Wortman was killed in a shootout with police in Enfield, about 60 miles from the initial crime scene, Leather said.

The motive behind the shooting, one of Canada's deadliest, is under investigation, Leather said. Wortman knew some of his victims, police said, while others were strangers.

23-year veteran of RCMP killed

One of those killed was Constable Heidi Stevenson. Another officer was hospitalized, the RCMP said on Facebook . The injured officer is recovering from gunshot wounds at home, police said.

"It is with tremendous sadness that I share with you that we lost Cst. Heidi Stevenson, a 23-year veteran of the force," said Lee Bergerman, the RCMP's commanding officer in Nova Scotia."Two children have lost their mother and a husband his wife. Parents lost their daughter and countless others lost an incredible friend and colleague."

The chaos began when police were first called to a "firearms complaint" at a Portapique property Saturday at 10:30 p.m. (9:30 p.m. ET).

Constable Heidi Stevenson had two children, police say.

"When police arrived at the scene, the members located several casualties inside and outside of the home," Leather said.

Investigators believe the incident began with a domestic violence incident at a home in Portapique, where Wortman was trying to find his former significant other, the law enforcement source familiar with the investigation said.

Wortman killed two people there before he fled, the source said.

The gunman was wearing either an RCMP uniform or a convincing replica, while driving a car that appeared to be a police vehicle, Leather said. Wortman was not employed by the RCMP, authorities said.

Wortman killed drivers he pulled over, source says

Upon fleeing the Portapique residence, it is believed that Wortman began pulling over random motorists and executing them, the law enforcement source said. After the gunman was involved in a traffic accident, he ditched the fake police cruiser and stole a vehicle from a motorist, the source said.

"His ability to move around the province undetected was surely greatly benefited by the fact that he had a vehicle that looked identical in every way to a marked police car," Leather said. "He was wearing a police uniform which, as I say, was either a very good fabrication of or actually a police uniform. That surely contributed to his ability to circulate."

Wortman was a skilled mechanic and enjoyed cars and motorcycles, neighbor BIll McCormack told CNN media partner CTV News . Wortman had recently bought two used police cars -- which McCormack described as "mountie cars" -- and kept them behind a clinic where he worked, he told the station.

"I never asked him about it," McCormack said.

After the initial notice that a gunman was on the loose, police warned residents to stay away from a campground in Glenholme, about 15 miles east of Portapique.

Police first asked the public to be on the lookout for the bogus police cruiser in Debert mid-morning Sunday.

One of the 18 victims, elementary school educator Lisa McCully, worked at Debert Elementary School, according to the Nova Scotia Teachers' Union, which described her a "passionate teacher" and a "shining love" in her friends' and family's lives.

Wortman was later seen in Central Onslow and farther south in Brookfield, where police updated the suspect's vehicle description to a silver Chevy Tracker.

'Oh my God, lock the doors! He's here!'

Wortman was involved in a "serious criminal event" in Shubenacadie, about 15 miles south of Brookfield, the RCMP's Serious Incident Response Team said.

Witnesses recalled hearing multiple gunshots in the area, according to CTV News

Several burned-out vehicles, which may have been police cruisers, sat along the highway, the station reported.

"I hear the shots and ... there's a guy running back and forth up beside what looks to be a police vehicle," a witness at the scene told the station. "Then after a short bit I saw fire."

Though it isn't clear where Constable Stevenson was killed, she and another officer tried to run Wortman's vehicle off the road at one point, the law enforcement source familiar with the investigation told CNN. Stevenson was killed and the other officer was injured in an ensuing exchange of gunfire, the source said.

Gabriel Wortman was killed in a shootout, police say.

Following the incident in Shubenacadie, Wortman continued south to Milford and was ultimately found at a truck stop in Enfield between 11 a.m. and noon Sunday, about 12 hours after the initial 911 call to police.

Truck driver Tom Nurani was at the truck stop when he heard a staff member frantically shouting, he told CTV News.

"'Oh my God, lock the doors! He's here!'" Nurani recalled the woman saying. "I peek out of the window, and I saw some RCMP vehicles, and there was four or five uniforms with guns."

Witness Glen Hines was driving past when he heard gunfire, he told the station.

"All I could hear was gunshots and my wife. I thought I was going to call 911 because she was going into panic, it scared her so bad," Hines said.

Politicians respond to shooting rampage

Nova Scotia Premier Stephen McNeil called the shooting spree "one of the most senseless acts of violence in our province's history."

"I never imagined when I went to bed last night that I would wake up to the horrific news that an active shooter was on the loose in Nova Scotia," he said.

"Our hearts go out to everyone affected by the shooting," Canadian Prime Minister Justin Trudeau tweeted.

"To the Portapique community, we're keeping all of you in our thoughts. And on behalf of all Canadians, I want you to know that we're here for you -- and we'll be here for you in the days and weeks ahead," he said.

Our hearts go out to everyone affected by the shooting in Nova Scotia. To the Portapique community, we're keeping all of you in our thoughts. And on behalf of all Canadians, I want you to know that we're here for you - and we'll be here for you in the days and weeks ahead. — Justin Trudeau (@JustinTrudeau) April 19, 2020

Orders issued to protect the public during the Covid-19 pandemic will prevent Canadians from mourning in person, he said, but a virtual vigil is scheduled for Friday.

The National Police Federation is "working hard to ensure all our members and their families are supported," federation president Brian Sauvé said.

"We are there for them now and will be there for them for the coming days and months as they work through this tragedy," Sauvé said. "As Canadians, we are extremely fortunate these incidents are not common."

A statement issued by the White House said President Donald Trump and first lady Melania Trump expressed their condolences.

"The United States and Canada share a special, enduring bond. As friends and neighbors, we will always stand with one another through our most trying times and greatest challenges," the statement said. "The United States strongly condemns these murders, and our prayers are with the victims and their families."

Trudeau promises to toughen gun laws

On Monday, Trudeau said his administration will move ahead with stricter gun laws.

"In regards to gun control, we took very serious commitments in the election campaign and have moved forward -- and are moving forward on them -- to ensure that we're strengthening gun control in this country," Trudeau told reporters, according to CTV.

While campaigning last year, Trudeau said he wanted to ban assault-style rifles and set up a buyback program for all military-grade weapons that had been legally purchased.

Authorities have not said what kind of weapons the gunman used in Nova Scotia.

"I can say that we were on the verge of introducing legislation to ban assault-style weapons across this country; it was interrupted when the pandemic caused Parliament to be suspended," Trudeau said.

CORRECTION: This story has been updated to reflect the suspect drove two different vehicles while on the run.