The 30-hour search for Justin Bourque came to a sudden end Thursday night soon after the arrival of an aircraft rigged with sophisticated surveillance equipment normally deployed to patrol the Canadian coast.

As police on the ground struggled to track the man alleged to have gunned down three Mounties, behind the scenes officials at Transport Canada told the RCMP they had a powerful asset in reserve. It turned out to be key to capturing the accused killer.

The aircraft, a DASH-8, is the workhorse at the centre of the National Aerial Surveillance Program. What makes it special is its sensitive camera, the MX-15, which is used to monitor shipping lanes and detect environmental spills. With an armed suspect on the loose, and with three officers dead and two others wounded, getting close to him on the ground was a risky proposition. Mr. Bourque had been spotted a few times early Thursday, but then seemed to slip away into a wooded section of North Moncton.

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Shortly after 1:30 p.m., the chief of intelligence, surveillance and reconnaissance at Transport Canada, Louis Armstrong, advised his team that the DASH-8 had been redirected to Moncton and was set to land within 35 minutes. It would be at the RCMP's disposal.

"I just spoke to Cst. Mike Oliver – J Division, to explain the capabilities of the Dash 8, mainly the MX-15," Mr. Armstrong wrote in an e-mail.

The MX-15 is described as ideal for medium-altitude covert intelligence, surveillance and reconnaissance missions. It can offer real-time imaging that shows a landscape in shades of grey. Anything with a heat signature, such as a human being, registers as a bright white. It's considered among the most sophisticated aerial imaging tools in the country.

With bad weather threatening, authorities decided to speed up their planned, midnight takeoff. At 11:24 p.m., Brad Mundle of Transport Canada sent an e-mail to colleagues, many of them part of the Marine Aerial Reconnaissance Team (MART).

"Transport 950 is airborne and over tasking area," Mr. Mundle wrote.

At 11:58 p.m., he updated the team again. The plane had spotted something: a heat signature coming from a wooded area. It's not clear whether the aircraft was directed to that spot beforehand based on intelligence developed on the ground. The RCMP would not comment on the specifics of the investigation, but did say that a citizen had provided information Thursday that contributed to the suspect's capture.

Mr. Mundle was watching it all from the aircraft hangar via live video. The MX-15 has the ability to blend infrared and electro-optic, night-vision images, making for a highly detailed, stable picture of what's happening on the ground, even in darkness.

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"We're apparently streaming a video that has everyone excited," Mr. Mundle wrote. "We are onto someone hiding in the bush."

Up in the air, an RCMP officer was in the cockpit with the Transport Canada pilot, passing information to police on the ground by radio. Meanwhile, RCMP commanders in the situation centre watched images relayed by satellite. What they could see, according to a source who was not authorized to speak on the record, was the shape of a man crouched behind a tree. Once the heat signature was spotted, the force's Emergency Response Team on the ground was ordered to move.

Less than 10 minutes later, the heavily armed RCMP team descended on the yard of a home on Mecca Drive belonging to the family of Michelle Thibodeau. The images relayed from the DASH-8 showed a circle of white figures with weapons raised creeping slowly toward the lone figure in the trees, encircling him. Finally, the suspect could be seen raising his arms and dropping to the ground.

At 12:23 am, Brad Mundle updated his colleagues again.

"Got him, confirmed," he wrote.

"Excellent!" replied director of flight operations Steve Buckles.

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With a report from Kathryn Blaze Carlson in Moncton