Former chief minister Michael Gunner’s electorate office was broken into overnight with windows smashed and extensive interior damage caused, NT Police said.

A 47-year-old man who is expected to be charged later today was arrested a short time after police were notified of the break-and-enter around 4:10am at Parap Place. It was unclear if any items or documents were stolen.

The NT Independent understands the man smashed his way into the electorate office with a sledgehammer, then targeted the furniture and “personal items” belonging to Mr Gunner with the hammer.

Following the attack on the office, the man then sat outside waiting for the police to arrive, sources said.

Mr Gunner said on Facebook that the unlawful entry was “a very personal break-in targeting photos of me and items of personal importance to me”.

“My staff are ok, my family are ok,” he wrote. “We’ll take advice from police on what our next steps may need to be to keep my family safe.”

It was unclear if any documents or items were taken during the break-in.

Mr Gunner further claimed in comments on Facebook that the break-in “appears to be a continuation of behaviour from a range of fixated individuals”, but the police have not suggested that.

Mr Gunner resigned from Parliament completely last week, triggering a by-election in Fannie Bay that has been scheduled for August 20.