TORONTO -- The horrifying details of a killer’s rampage through a 150-km swath of Nova Scotia show he was able to use his disguise as an RCMP officer to knock on doors, pull over cars and ambush the two officers he shot.

He killed 22 people, injured three more and left 16 crime scenes in his wake.

But significant evidence has been lost because Gabriel Wortman set fire to his home and garage in Portapique, N.S. and it burned to the ground, police said at a news conference Friday morning.

RCMP confirmed that before the mass killing began, the attacker restrained and beat a woman he was in a relationship with at his home in Portapique, N.S. on Saturday night before she escaped him and hid until daybreak Sunday in the woods.

That assault "could very well have been the catalyst" that unleashed his rampage, Supt. Darren Campbell said at a news conference Friday, but police are not ruling out that significant pre-planning was involved.

The woman, who is recovering and is co-operating with police, confirmed to investigators that the shooter was driving a replica RCMP vehicle and was wearing a police uniform.

Investigators are tracking how he managed to secure police equipment, including decals for a cruiser, lights for the roof, uniforms and other equipment. But Campbell said they do not believe that the killer had access to police radio equipment that would have allowed him to track police movements.

The RCMP outlined the details surrounding the death of one constable and the wounding of another.

Campbell says investigators have determined that RCMP Const. Chad Morrison and Const. Heidi Stevenson, both working out of the Enfield detachment, had arranged to meet at Hwy 2 and Hwy 224. When a vehicle approached, Morrison believed it to be that of Stevenson.

The gunman opened fire on Morrison, who was hit several times. He managed to drive away while notifying dispatch and other officers he had been hit.

Meanwhile, Stevenson was travelling northbound on Hwy 2 when the gunman crashed into her vehicle head-on. He fatally shot the veteran constable and stole her weapon and ammunition. He set fire to both vehicles and then killed a passerby who stopped. He escaped in that victim’s SUV.

THE INVESTIGATION

Neighbours told police that Wortman had significant weapons on his property. He used both long guns and a handgun in his rampage. One weapon has been traced to origins in Canada, while the remainder appear to have been obtained in the United States, says Campbell. But it’s not clear how those weapons were brought into Canada.

Police have also accounted for four vehicles owned by the killer that were made to look like police vehicles, Campbell revealed. He used one unplated car in his attack but possessed three others that carried licence plates. Two of them were destroyed in the fire on his property and another was found at his Halifax residence.

Campbell said as the crisis unfolded police didn’t know key information, including whether more than one gunman was involved. They deployed tactical teams, crisis negotiators, canine teams, bomb squads, and helicopters. Police were trying to search for the suspect while also searching for additional victims, rendering first aid, canvassing neighbours, and managing multiple crime scenes.

While police were able to narrow down a suspect “fairly early into our involvement,” said Campbell, the shooter’s ability to disguise himself as an officer made the police challenge much more difficult. He said police did not confirm that their suspect was in a replica police cruiser or wearing a uniform until they interviewed his girlfriend after 6:30 a.m. Sunday when she called 911.

In 30 years as a police officer, Campbell says he “can’t imagine any more horrific set of circumstances than when you are trying to search for someone who looks like you.”

He declined to talk about what investigators might know about potential motive, saying that will be something they will “continue to unpack for a very long time.”

When asked about why an emergency alert was not issued, Campbell says incident commanders didn’t have the benefit of hindsight while managing a complex situation. They thought they were dealing with a “localized incident” and that, on Saturday night, they had the area they believed the suspect was in “heavily locked down.”

Police also thought they had accounted for all the police-type vehicles the killer had in his possession. They were, at the time, unaware of a fourth car he was actually travelling in.

In addressing the concerns of loved ones of victims about the RCMP’s use of social media rather than the provincial emergency response system to alert residents about the gunman, Campbell said: “We hear the families of the victims full force. They have every right to ask these questions and they have every right to be angry.” Nova Scotia Premier Stephen McNeil said Wednesday the RCMP was contacted by the province's Emergency Management Office “a number of times” about issuing an emergency alert.

Campbell said the RCMP works hard to build trust with those they serve but that trust is easily lost.

“We are always looking to do better.”

Police are asking the public with any information, including photos and videos, to call a dedicated tip line at (902) 720-5959.

"No piece of information is too small," said Campbell. He said police are trying to fill in the killer’s whereabouts and activities during the 13-hour manhunt.

"If you have information, we need to hear from you."

Other new details revealed Friday morning:

Police believe the killer escaped road barriers set up in Portapique, where 13 people were discovered dead at seven locations, by driving through a field. Investigators did not know a car had been witnessed escaping through a field until later, Campbell said. That allowed him to travel him about 100 km and to kill a further nine people.

Campbell says, contrary to a report in the Globe and Mail, they have not uncovered a hit list created by the killer. He says that report, based on information from a neighbour, may stem from police contacting people they believed may have been at risk and removing them to safety. They were then interviewed by police to gather information.

While much evidence that may have been in the killer’s home has been destroyed, police did recover pieces of a uniform he was wearing. Investigators say he stopped to change clothes about 30 minutes before he was killed by police.

Campbell says they appear to be discarded or old pieces of uniforms, including one item from another police agency.

Nova Scotia’s police watchdog, the Special Investigation Response Team, is probing an incident in which two RCMP officers opened fire at a firehall that was being used to house residents who had been evacuated from their homes. The shooter was not believed to be in that area at the time.

CTV News has learned the officers thought another RCMP officer was, in fact, the shooter and only stopped firing once the other officer identified himself.

Campbell said he couldn’t comment on the incident except to say officers knew the killer was driving a marked vehicle.

He added: “I know that this entire incident, obviously is particularly difficult for every Nova Scotian. Certainly horrific for the families. And it's also a traumatic incident for all of the first responders and I'm not just talking about the police officers I'm talking about the ambulance attendants and the firefighters, our dispatchers, our officers and also the public as well.”

THE TIMELINE

Nova Scotia RCMP Supt. Darren Campbell presented a detailed account of 51-year-old Gabriel Wortman’s deadly path Friday.

The RCMP timeline begins with the police arrival to a call about a shooting at 10:26 p.m. Saturday in Portapique, where the shooter had a residence. In total, 13 victims were found at eight locations on Portapique Beach Road, Orchard Beach Road, and Bayview Court.

Investigators say the gunman then travelled about 43 km north to Wentworth where a shooting incident occurred at 9:35 a.m. Sunday. He then drove 30 km southeast to Debert, claiming more victims at 10:08 a.m., and then another 51 km south to Shubenacadie, where he killed more people at 10:49 a.m. The final stop was 24 km southwest at Enfield, where the gunman was killed by police at a gas station at 11:26 a.m.

Those new timeline details confirm that multiple victims died within the more than two-hour gap between when police learned of Wortman’s police uniform and lookalike RCMP cruisers from his girlfriend — a time police have estimated between 7 a.m. and 8 a.m. — and the time they warned the public of the disguise via Twitter at 10:21 a.m.

RCMP Chief Superintendent Chris Leather said Wednesday that police issued the tweet as quickly as they could.

“The information about the vehicle, the clothing, took some time to learn from the one witness and once that information was compiled, it was immediately tweeted by our communications section,” Leather said

Campbell said Friday that a full review will take place, as is the protocol with critical incidents.

In Portapique as the horrifying night began, police first made contact with a man who said he had been shot by someone in an oncoming vehicle. That man, who survived, was able to tell police the vehicle looked like a police cruiser and that the suspect was headed toward the beach. Police set up a perimeter, knowing there is only one road in and out of that area.

First responders then found deceased victims, some of whom were on the road. There were also a number of buildings on fire.

Campbell said the shooter killed two men and one woman in a home on Hunter Road in Wentworth more than 40 km away from Portapique and then set the residence on fire. Police say he knew at least two of the victims there.

The killer then travelled to a home on Highway 4. He knocked on the door but the residents, who knew him did, not answer. They called 911 and reported his identity, and told dispatchers he was armed and driving what looked like a police car. He did not fire his weapon.

The gunman continued southbound on Highway 4 from Wentworth to the Glenholme area. On the way, he came upon a woman who was out walking and shot her. Witnesses said he then pulled over a vehicle and shot its driver before he continued down the highway and shot another driver.

He then encountered and shot Const. Chad Morrison and then rammed the vehicle he was driving head-on into the cruiser driven by Const. Heidi Stevenson. She was then fatally shot. Her weapon and ammunition were taken by the gunman, who then torched both vehicles.

A passerby who stopped at that scene was fatally shot and the killer escaped in that victim's SUV.

He travelled a short distance to the home of a woman he knew on Highway 224. He killed her before stealing her Mazda 3. He transferred his weapons to that car, stopped to change out of the police clothing he had been wearing, and then pulled into a gas station in Enfield, N.S. A tactical officer, who had stopped to refuel, killed the gunman there.