The attack happened at a flat in the Enler Park area of Dundonald on Monday, December 18.
Detective Constable O’Neill said: “ It was reported to police that four masked men, one armed with a firearm and three others armed with bats, forced entry to the flat at around 10 pm on Monday night.
“The 19 year old male occupant of the flat was threatened by the men who then smashed windows and furniture before leaving.
“There were no reports of any injuries.”
“I would appeal to anyone who may have witnessed this incident or anyone who has information which could assist us with our enquiries to contact detectives at Lisburn on the non-emergency number 101 quoting reference 1467 18/12/17.
“Alternatively, information can also be provided to the independent charity Crimestoppers on 0800 555 111 which is 100% anonymous and gives people the power to speak up and stop crime.”