A man was arrested at the airport after firing as many as five shots inside, some leaving bullet holes in airport windows, just after 1.30pm on Sunday.
The man was taken to a Canberra police station, with the firearm seized by officers.
Police are yet to establish a motive behind the incident, but ACT Detective Acting Superintendent Dave Craft said the shots were not aimed at anyone.
Officers are yet to provide a name or age of the man, but Det Supt Craft said he was believed to be the only person responsible for the incident.
Det Supt Craft said the man did not go through airport security and sat near the check-in counters before firing shots at the windows.
The airport was evacuated shortly after the shooting incident, with parts of the terminal locked down.
Passengers who had boarded planes were stuck on the tarmac for hours before being allowed to disembark.
The airport resumed normal operations before 5pm. "Please check your travel plans directly with your airline if you are travelling today," its management said in a tweet.
Police said there was no ongoing threat to the community or to other passengers.
Prime Minister Anthony Albanese said he had been briefed on the airport incident.
Finance Minister and ACT senator Katy Gallagher said she had been shocked by the event.
"Our local airport is such an important part of the Canberra community and it must have been terrifying for everyone," she said on Twitter.
"Thanks so much to the first responders for keeping everyone safe."
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