On the afternoon of 12 April, Oldeberkoop was liberated by "D" Squadron of the Royal Canadian Dragoons. Later that day, they established a temporary headquarters in the village. The movements of "D" squadron were coordinated from the headquarters. This was also the place where prisoner of war from the immediate surroundings were gathered.  

These prisoners of war were often Germans, but sometimes also Dutch who served voluntarily in the Waffen-SS, the NSKK (a paramilitary section of the Nazi party NSDAP) or the Dutch Landwacht. On this 12th of April, ten of these collaborators were brought into the encampment in Oldeberkoop amid great interest. Hatred of people who fought with or for the Germans was strong among most of the Dutch population. A resident of Oldeberkoop described the moment the men were brought in:  
 
"The crowd booed and whistled, some spat, and some could not keep their hands off them. One of them got such a blow to the head that hit made his head spin."  

Not much later, these POWs were taken away again. Presumably with the aim of taking them to a real prison camp in Vledder. But the men would never get there. All ten of them were shot without trial in the Koepelbos just outside Oldeberkoop.  

It was long thought that the Canadians were responsible for these unlawful executions. But by 1995, it became clear that Canadian involvement had been minimal. Stories about the involvement of two former resistance fighters were confirmed when one of them confessed to having fired the shots. In addition to himself, a colleague, a Canadian driver and some men who had dug the graves were present at the execution.  

The exact reason for the murder of the Dutch collaborators and the exact role of the two Dutchmen and the Canadian have never been fully clarified. There are different accounts of the events leading up to the shooting. On 14 April, the bodies were finally buried in a mass grave on the side of the road. Later they were transferred to the German war cemetery in Ysselsteyn. The names of most of the victims also became known at that time:   

 
Egbert Jan Hommes, Ordnungspolizei  
Otto Frikken, Ordnungspolizei  
Gerrit Jan Seevinck, Dutch Landwacht  
Hendrik Dales, Dutch Landwacht  
Heike Ham, Dutch Landwacht  
Douwe Jonkman, Dutch Landwacht  
Bernard Janssen, Dutch Landwacht  
Arnold Pieter Post, Dutch Landwacht  
The identities of two men from the Dutch Landwacht could not yet be ascertained.