When many of the Vets came back from the War, the government didn't know what to do with them so they were all thrown into the Post Office. That was before PTSD was recognized by the medical community.
And the term Going Postal was born.
Even though there hasn't been any major Canada Post incident of an employee going bonkers with a weapon in over 80 years, the term still sticks. We had a mass shooting at OC Transpo in the Nation's Capital a number of years back. They should call it , 'Going Transpo' instead