HALIFAX -- Police say at least 18 people, including an RCMP officer, have been killed in a mass shooting incident in Nova Scotia, making it the worst mass shooting in Canadian history.

The suspect is also dead following the incident.

RCMP commissioner Brenda Lucki confirmed the number to CTV News Monday morning.

The Nova Scotia RCMP also provided an update during a news conference in Dartmouth, N.S. Sunday evening.

“Today is a devastating day for Nova Scotia and it will remain etched in the minds of many for years to come,” said commanding RCMP officer Lee Bergerman.

“What has unfolded overnight and into this morning is incomprehensible and many families are experiencing the loss of a loved one.”

Police confirmed that Const. Heidi Stevenson, a 23-year veteran of the Nova Scotia RCMP, died Sunday morning while responding to the active shooter incident.

"Heidi answered the call of duty and lost her life while protecting those she served," said Bergerman. "Two children have lost their mother and a husband has lost his wife. Parents have lost their daughter and countless others lost an incredible friend and colleague."

A male RCMP officer was also taken to hospital with non-life-threatening injuries. His identity has not been released.

"He and his family will be supported and we will be alongside him as he begins his road to recovery," said Bergerman.

Several people found dead at Portapique home

Chief Supt. Chris Leather said police first responded to a firearms complaint at a residence in Portapique, N.S. late Saturday evening after receiving several 911 calls.

When officers arrived, Leather said they found “several casualties” inside and outside of the home.

“This was a very quickly evolving situation and a chaotic scene,” said Leather, the criminal operations officer for Nova Scotia RCMP.

Officers secured the area in Portapique and started searching for the suspect, but they were unable to locate him.

Leather said the search for the suspect led to several sites in the area, including structures that were on fire.

“The search continued overnight and into the morning,” said Leather. “This morning we actively sought out the suspect through multiple communities throughout Nova Scotia.”

Police provided updates on Twitter overnight and into Sunday morning as they tracked the suspect across the province. Police confirmed that they were responding to an “active shooter situation,” and asked residents to remain in their homes with their doors locked.

Investigators first released the suspect’s identity before 9 a.m. Sunday. They said 51-year-old Gabriel Wortman was considered armed and dangerous and warned that he should not be approached.

Suspect travelled in vehicle resembling RCMP cruiser

Police said that, at one point, the suspect was driving what appeared to be an RCMP vehicle and wearing an RCMP uniform -- though he was not an RCMP officer.

Leather said the fact that Wortman had an RCMP uniform and a vehicle resembling a police cruiser indicates that the incident may have been planned.

“That’s an important element of the investigation,” said Leather. “The fact that this individual had a police car and a uniform at his disposal certainly speaks to it not being a random act.”

They later said he was driving a silver Chevrolet Tracker.

Police continued to track Wortman across the province, warning the public about sightings in Glenholme, Debert, Brookfield and Milford.

Victims were ‘scattered across the province’

Leather said the investigation involves “multiple crime scenes” and that there are victims “scattered across the province.”

“There are several locations across the province where persons have been killed,” said Leather.

He said one person is believed to be responsible for the killings.

“He alone moved across the northern part of the province and committed, it would appear, several homicides,” said Leather.

He didn’t specify where the crime scenes are located, saying the investigation is in the early stages. He also said it’s possible police could learn about additional crime scenes and victims in the coming days.

“Some of these crime scenes we’ve not even begun to process … it is an ongoing investigation that could reveal additional details in the coming days,” said Leather.

“The investigation continues into areas that we’ve not yet explored across the province.”

In Shubenacadie, N.S., there were several burned-out vehicles, which appeared to be police cruisers, along the highway. Witnesses also reported hearing between seven and 10 gunshots.

“I hear the shots and I look out and … there’s a guy running back and forth up beside the, what looks to be a police vehicle,” recalled one witness at the scene. “Then after a short bit I saw fire.”

Leather confirmed that Wortman did exchange gunfire with police at one point during the chase, but wouldn’t say where.

Suspect shot and killed in Enfield

Officers eventually tracked Wortman to the Irving gas station and Big Stop restaurant in Enfield, N.S., where he was shot and killed late Sunday morning.

Leather wouldn’t confirm that Wortman was shot by police, but he did say “officers were involved in terminating the threat.”

He also confirmed that Nova Scotia’s Serious Incident Response Team -- which investigates serious incidents involving police -- is investigating the man’s death.

Witnesses heard gunshots, saw body on the ground

A truck driver from Ontario told CTV News he had stopped at the Irving for a shower and breakfast when he heard an employee shouting.

“She goes, ‘Oh my God, lock the doors, he’s here! And I peek out of the window and I saw some RCMP vehicles and there was four or five uniforms with guns,” said Tom Nurani.

Witnesses told CTV News they saw RCMP vehicles on scene, heard multiple gunshots, and saw a body on the ground.

“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,” said Glen Hines, who was driving by the Irving when he saw the Emergency Response Team arrive.

“There was multiple, like probably between five or 10 (gunshots). It was steady,” recalled Deon Wells, who lives nearby.

The RCMP had blocked off Highway 102 at Exit 5A and there was a large police presence at the Big Stop all day Sunday. The area surrounding the restaurant and gas station was cordoned off with police tape.