Twenty years after a Montreal police officer was killed during a routine traffic patrol, his murder remains unsolved.

Const. André Lalonde, a police officer with what was then known as the Montreal Urban Community Police Service, pulled over a car with a broken muffler in Senneville, Que. at around 10:15 a.m. on April 29, 1996.

Witnesses at the time said Lalonde calmly got out of his car and was about to ask for the driver's licence and registration when he was shot three times.

He was pronounced dead a few hours later at Lakeshore General Hospital. He was 51 years old.

Lalonde was married with two kids, had served more than 29 years with the MUC police force and was just two months away from retirement.

Lalonde's funeral was attended by thousands of police offers from across Canada and the United States.

Unsolved murder 'not common'

Montreal police Cmdr. Ian Lafrenière said having an unsolved murder of a police officer still on the books is extremely uncommon. The only other unsolved case he could think of was that of Const. Odette Pinard, who died the year before in 1995.

"It was quite a shock," Lafrenière said of Lalonde's murder.

Lafrenière, a young police officer at the time and one of the first people at the scene, remembers that day as a "nightmare."

The shooter, who police said was a white man around 25 years old, got away in what was later revealed to be a stolen vehicle. The car itself was found torched and abandoned on Beaumont Street near Parc Avenue later that day.

Police arrested a 32-year-old man a day later, but then said he was not connected to Lalonde's murder.

MUC police and Sun Youth volunteers even teamed up in July to post flyers offering up a $25,000 reward for information leading to Lalonde's killer.

"We've got nothing new unfortunately on André Lalonde" Lafrenière said, adding that the case is still considered an active investigation.

"An unsolved murder is never closed."

Lalonde's partner also killed

Lalonde had another brush with death in the line of duty almost 20 years earlier.

In 1974, Lalonde and Const. Aimé Pelletier, responding to an armed robbery call on St-Laurent Boulevard, found themselves chasing down three suspects.

Pelletier was shot in the back and returned to his police vehicle to frantically call for backup.

Lalonde found his partner dead in the front seat, police radio in hand.

His killer, Arthur Gagnier, was on the run from Cowansville prison after he was released for an authorized visit.

An annual memorial will be held in May during police week to remember those who died in the line of duty like Lalonde, Pelletier and Pinard.

"It's important to remember officers that have fallen," Lafrenière said.​