UPDATE: The slain officers have been identified as constables Fabrice Gevaudan, 45, Douglas Larche, 40, and David Ross, 32.
It was the force's worst loss of life since 2005, when four Mounties were ambushed on a rural property in Mayerthorpe, Alta.
Including the Moncton officers, 90 Mounties have been killed by gunfire since 1865.
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One of the worst cases happened in 1935. Constables John Shaw, 39, and William Wainwright, from the municipal force, were driving three men in for questioning about an armed robbery. They were attacked with a knife from the back seat. In the struggle, the suspects got Wainwright's gun and shot him in the eye. Shaw was shot in the head. The officers' bodies were dumped in a field.
The three killers — farmers' sons aged 18 to 21 — were stopped at an RCMP roadblock as they tried to enter Banff. Two more Mounties, Const. George Harrison, 29, and Sgt. Thomas Wallace, 39, were killed.
The trio fled into the bush but were shot to death.