Police radio dispatches aired Thursday reveal the chaos of a 14-hour manhunt for a killer impersonating a policeman in Canada's worst ever mass shooting.

In the aftermath of the weekend shooting and arson spree that left 22 dead in Nova Scotia, the Royal Canadian Mounted Police (RCMP) has come under fire over what is described as its poor public communications.

The recordings and a surveillance video clip, broadcast by news organizations, track the killer's trail through several towns.

The drama began with a call to a police emergency number at 10:26 pm on Saturday about a shooting.

Within minutes, police responded. "We're seeing huge flames and smoke from where we are," a policewoman is overheard saying over a police scanner.

That is quickly followed by an account of fatalities and "GSW" or gunshot wounds, along with a request for ambulances.

A man named Clinton Ellison told public broadcaster CBC he'd gone to look for his brother who had gone out to check on the fires and failed to return.

Stumbling over his brother lying dead in a pool of blood in the darkness, Elison said he saw someone believed to be the killer scanning the area with a flashlight.

Ellison said he ran into the forest and hid.

"I was laying there for hours and all I could hear were explosions from the fires and gunshots coming from all around me," he said. "It was the most terrifying thing I've ever experienced in my life."

Police have said some of the victims were targeted, while others were killed at random.

The Globe and Mail said the gunman, identified by police as 51-year-old denturist Gabriel Wortman, had drawn up a hit list.

Photo: NOVA SCOTIA RCMP / Handout

The paper quoted an unnamed man who said investigators had told him he was "seventh or eighth on the list" later found at Wortman's home.

At 11:21 pm, an officer asks if the suspect has been caught. A police dispatcher replies: "They don't know if they've caught him."

Minutes later, police tweet about a shooter on the loose. Many have questioned why an emergency alert was not issued to warn the public.

"I don't use Twitter, and I don't know anyone that does use Twitter," Nick Beaton told CTV. His wife, a nurse, was killed by the shooter on her way to work Sunday.

On Wednesday, RCMP Chief Superintendent Chris Leather defended the force, saying its messaging had been "the best and clearest information that could be provided."

Police were in the process of preparing an emergency alert when the crime spree came to an abrupt end, he added.

The killings had continued through the night with attacks in the town of Wentworth and down a highway.

Early Sunday, the RCMP learned from a witness that the suspect wore a police uniform and was driving a mock squad car.

Surveillance video captured him stepping out of his replica police car in a parking lot and calmly putting on a yellow vest, before driving away.

Fifteen minutes later, Constable Heidi Stevenson located and rammed the suspect's vehicle head on.

A witness said the shooter walked over to her cruiser after the crash and fired several shots into the vehicle, taking the life of the veteran police officer.

Both vehicles were set on fire, and the suspect fled in a third hijacked vehicle.

A police helicopter radioed at 11:14 am, "We're just overhead vehicle fire at the intersection of Highway 2 and (inaudible). Looks like there might be a police car involved. There's other police vehicles there."

Minutes later, the pursuit continued to a gas station outside Halifax where the gunman was shot dead by police, 100 kilometers (62 miles) from the site of the initial attack.