The attack happened last week, when Douglas Andrew Tilley, 33, knocked a mental health worker to the ground and then kicked him, breaking a cheekbone and badly bruising him.
Tilley had already written threatening emails to two West Kootenay doctors in early October, and staff say he had previously come into their reception area ranting and pursued employees outside the building.
Twenty-six people work at Nelson's mental health office and some tell the CBC they are terrified. They say Tilley was obviously dangerous and Interior Health did nothing to protect staff.
Frightened staff say there was no safety protocol put in place or even a picture of the threatening man circulated.
Interior Health said the safety and security of their staff is paramount and they will investigate the incident along with Worksafe BC.
Meanwhile, Tilley pleaded guilty on Tuesday to aggravated assault and uttering threats. He was given a six-month sentence and two years' probation.
He apologized to the court for the assault and said he is "full of rage."