A disgruntled former public servant has pleaded guilty to storming a southside government office with a chainsaw as payback for perceived ill treatment by management.
Benjamin Dunne, 35, had an appointment with ACT Mental Health on the afternoon of March 28 last year.
But he skipped the meeting and instead launched the assault on the Department of Human Services offices in Greenway.
Dunne, 35, pleaded guilty in the ACT Supreme Court on Friday to committing an act to cause public alarm.
The offence carries a maximum of 10 years jail.
A charge of damaging Commonwealth property was dropped as a result.
Dunne will also face a scheduled offence of possessing an offensive weapon with intent when he is sentenced next month.
Terrified staff dashed for cover when Dunne, who was subject to a psychiatric treatment order at the time, attacked the office.
Court documents said Dunne had worked at DHS but left the job on bad terms.
As payback, he formulated a plot to scare his former colleagues at Flax House.
He bought a chainsaw, with a 30 centimetre bar, from Bunnings and posted hints on social media about his plans, including "Pathetic they could have saved lives".
He told his housemate, who later called police, that he would never see him again and caught a taxi to Tuggeranong.
About 3.38pm he ran into the Cowlishaw Street building with the chainsaw.
Once inside he started the weapon and violently struck a glass security door until it shattered.
DHS employees saw the offender hitting the door and fled the building through emergency exits.
Police found and arrested Dunne holding the still running chainsaw in a corridor between office cubicles.
He told police at the time he had gone to the building to get a confession from two managers that he said were responsible for damage to his home.
Dunne was taken to hospital for mental health assessment and later made admissions to police.
Dunne said, during a police interview, that he wanted to make a manager “shit his pants”.
Chief Justice Helen Murrell abandoned a scheduled trial date and ordered a pre-sentence report be prepared ahead of the April sentence hearing.