Diane Dery and Mario Corbeil – The Murder Weapon

Last summer Radio Canada’s Ici Tou TV aired a five-part documentary, Le Dernier soir about the 1975 murders of 13-year old Diane Dery and 15-year-old Mario Corbeil. Recall that the two youths went missing one May evening when Mario offered to give Diane a ride on his new motorbike. Their bodies were found the following morning in a field not far from their homes in Longueuil. Mario had been shot six times, Diane twice.

Last year I did a podcast on the case in which I speculated that Dery and Corbeil were most likely killed by a member of the Canadian military. The chief reasons being, 1. the proximity of an air force base adjacent to the dump site. 2. The police revealing to the media at that time that the murder weapon was a .22 caliber “pistolet”. 3. The nature of the murders suggested a mature assassin.

It turns out I was wrong. One of many interesting things Le Dernier soir reveals is that the murder weapon was in fact a .22 calibre Sure-Shot Cooey, model 64, semi-automatic rifle. Episode two of the documentary goes into great detail about the Cooey rifle, ballistics, possible trajectories, positioning of the assassin(s), etc….

In the final episode, Le Dernier soir suggests that Dery and Corbeil were murdered by a teenager or a group of teenagers who were possibly jealous of Mario’s relationship with Diane. Their prime suspect is an at the time 17-year-old school mate of Mario who went on to become a prominent member of one of Quebec’s motorcycle gangs. When the show ends we find this individual living in France, having been deported by the Canadian government in 1988. At the time of the murders this individual owned a Cooey rifle.

So why the confusion between the .22 “pistolet” and rifle? As it turns out, this may have been a classic case of the Longueuil police issuing false information to protect their investigation. In the 1970s, the Cooey Sure Shot was a very popular hunting rifle for teenage boys. Police knew that several young men in that Longueuil neighborhood owned Cooeys. The area was surrounded by woods. Young men would typically enter the forest and practice their marksmanship on local gaming birds and water fowl. There was some speculation that Diane Dery was shot first, knocked right off the back of Mario’s bike, quite a feat to hit such a moving target, but if you had practiced on pheasants and ducks, not impossible. Police knew that if they went public with the Cooey information then everyone in the neighborhood would likely dispose of these weapons. So they held back this information.

I was interviewed for Le Dernier soir. I think I appear in episodes two and four. One of the points I made – and this never made it in the final version – was that the Cooey Sure Shot was indeed a rifle marketed to young boys at that time. Here is a Canadian Tire ad from La Presse just before Easter weekend 1975 – 6 weeks prior to the murders – promoting a Cooey .22 rifle, just above the Cooey we see notices for kids’ bicycle horns and banana seats:

Cooey Canadian Tire ad, La Presse – March 24, 1975

In December 1975 a Cooey .22 is featured in the Eaton’s Christmas catalogue. The rifle at the top is the Cooey, equipped with a high powered scope. The Cooey that killed Dery and Corbeil most likely had a similar scope, if it were to take down a moving target:

Cooey Sure Shot

The page before the Cooey rifle in the catalogue features boys hockey equipment, and you can see on the same page as the Cooey a “play wigwam teepee”.

Cooey Sure Shot in Eaton’s catalogue – Christmas 1975

Contrary to the argument that only a mature assassin could have been responsible for the murders of Diane Dery and Mario Corbeil, the rifle evidence suggests very likely that the killer or killers were much younger.


2 thoughts on “Diane Dery and Mario Corbeil – The Murder Weapon”

  1. In one of the episode it was mentioned that Mario had bruises on his knuckles suggesting a fight had taken place before being shot.Why no one noticed who had bruises on his face.
    A possible scenario is that the girl was hit by accident, then a fight between the shooter and Mario which ended when he was shot and than to eliminate the witness, the girl was also shot.

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