A rookie Mountie from New Brunswick is being praised for helping nab a convicted killer considered to be one of "America's Most Wanted" fugitives.

After nearly 18 months on the run, Richard Lee McNair, 48, was arrested in Campbellton, N.B., shortly after noon on Thursday.

"You have captured a big fish," McNair told officers, according to the RCMP in a Friday news conference in which they revealed details of the arrest.

The RCMP say it all started when an off-duty police officer spotted a white van on Wednesday. It had darkly-tinted back windows and the officer suspected it might be involved in smuggling across the nearby border between Maine and Quebec.

Rookie Const. Stephane Gagnon and his field coach, Const. Nelson Levesque, saw the van the next day, with McNair behind the wheel. During a brief pursuit, the van turned onto a dead-end road and the driver tried to run away.

He only got about 400 metres before Gagnon, who had been on the force for only six weeks, tackled him and made the arrest.

"I put my hands on his back and fell to the ground with him," said Gagnon.

At first, McNair resisted, but not for long.

"In the first yes, but after with Const. Levesque, we began to control him and put handcuffs on him," said Gagnon, a Quebec City native.

Gagnon and Levesque say they had no idea that they had nabbed one of America's most wanted.

"At that time he told me we all got a big fish," said Levesque.

After reading McNair his rights, he told the officers what he had done in the U.S.

"I confronted him about the Alaska driver's licence that he produced and he said 'Well, it's all false'," said Levesque. "He said 'My name is Richard Lee McNair.' He said: 'Look it up and you'll see what I am about'."

Levesque said it was only after checking with Canadian and U.S. authorities that they realized just how big "a fish" McNair was.

American authorities had high praise for the Mounties on Friday. One police officer who had been chasing McNair said he's even considering naming one of his future children 'Stephane' in honor of Gagnon.

Police said it appeared McNair had been living in the white van, which was stolen in Ontario. Inside the van, they found computer equipment that they suspect may have been used to make fake identifications.

Insp. Roland Wells said investigators were examining the van.

"We're having them look at the computer equipment in the vehicle, we're having them look for all physical evidence that's there," he said.

"We're not letting this guy leave the country until we're sure that nothing more serious has happened here that we're not aware of yet."

America's Most Wanted correspondent Michelle Sigona told CTV Atlantic that McNair's apprehension is a major victory for all law enforcement officers.

"This is huge," she said, adding that he was listed by federal marshals as one of the 15 most-wanted criminals in the United States.

"You figure, we have hundreds of thousands of fugitives and for him to be one of the top 15 in the U.S. is a very big deal," Sigona said Thursday.

In 1988, McNair pleaded guilty to the murder of truck driver Jerome Theis of Circle Pines, Minn. Theis was shot to death during a burglary at a Minot grain elevator in 1987.

In April 2006, while serving three life sentences in a Louisiana prison, McNair escaped by hiding in a pile of repaired mail bags that were later shrink-wrapped and shipped to a nearby warehouse.

McNair has since been transferred to the Atlantic Institution in Renous, N.B.

Authorities originally thought the fugitive would seek refuge in Mexico, but three weeks after his escape, RCMP in Penticton, B.C., found him sitting in a stolen car. He fled from B.C. authorities and was then spotted in southern Alberta, prompting Calgary police to join in the hunt.

America's Most Wanted correspondent John Morris told Canada AM on Friday that authorities knew McNair was in Canada, but believed he was still hiding in a Western province.

"We profiled him on America's Most Wanted 11 times since he escaped in April, 2006. We had over 1,000 tips over the last year on Richard McNair and over 300 of those came from Canada," Morris said from Washington.

"We had him filmed at a Blockbuster (in Canada) and we knew he was there but we didn't know he had traversed all the way across Canada and was in New Brunswick until Thursday," Morris said.

Morris said McNair is known for being one of the craftiest escape artists in the country and made several attempts over the last two decades to elude authorities.

In February 1988, McNair was first taken into custody in North Dakota. When he asked to go to the washroom, police thought to frisk him one more time.

"When they did, they found he had a concealed handgun on him that had been missed on the first frisk when he was taken into custody," Morris said.

That same day, he used a tube of lip balm to grease his hands and slip out of handcuffs at the Minot police station. He was apprehended after he jumped from the third floor of a building near the local hospital.

His second escape occurred at the North Dakota State Penitentiary. Officials said McNair and two other prisoners escaped through a ventilation duct on Oct. 9, 1992. He was captured the following July in Grand Island, Neb.

He also escaped from the Ward County Jail while awaiting trial for the grain elevator shootings.

With a report from CTV Atlantic's Andy Campbell and files from The Canadian Press