The decision comes after Benjamin Dunne's family said ''mental health services failed him'' by refusing to admit him to the psychiatric unit in the past fortnight, despite their pleas.

At the ACT Magistrates Court on Saturday, Dunne was charged with three offences, including acting with intent to cause public alarm, after he allegedly attacked the Department of Human Services' Greenway office in Cowlishaw Street with a running chainsaw.

His lawyer told the court his client wanted to go to hospital.

Magistrate Beth Campbell sent Dunne to the psychiatric unit under section 309 of the Crimes Act, which allowed the court to order urgent mental health assessments for defendants.

The 34-year-old Dickson man, who is understood to be a former DHS employee, allegedly smashed a glass security door, causing extensive damage.

Terrified staff reportedly ran on hearing of the intruder, with some cowering in cupboards before escaping to the safety of the Tuggeranong library.

A stream of triple-0 calls alerted police to the drama and the man surrendered when officers arrived shortly before 4pm.

No one was injured during the incident and Dunne's family apologised on Saturday to those caught up in the mayhem.

His mother said her son's mental health had declined in recent years, to the point where he had cut off contact with his friends and family.

''Mental health services have been contacted in the past two weeks in regard to communications from [my son] and related concerns he was acutely unwell and yet again failed to act on those concerns.''