A federal officer’s gun was “unintentionally discharged” in a busy airport terminal on Wednesday morning, bringing it to a standstill.

The Australian Federal Police are now investigating how the short-barrelled rifle came to be fired.

There were earlier reports a member of the public had tried to take a firearm from a police officer at Sydney Airport‘s domestic terminal, and the weapon had discharged during a struggle — sending the terminal into lockdown.

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Witnesses reported hearing a loud bang, and video obtained by Sydney radio station 2GB showed a person being restrained on the ground by officers.

Earlier reporting by 2GB said that the arrested man had attempted to take the AFP officer’s gun.

Former police officer dog handler turned barrister William Wilcher was with a former colleague at the domestic terminal to board a flight when the incident broke out.

“As we went past the coffee shop at the Jetstar terminal, there was a commotion between a tall man and two AFP officers,” he told 7NEWS.

“They attempted to arrest him, it appeared to me, the AFP officers were having some difficulties.

“We went to assist, a police firearm somehow found itself to be on the ground, the man was then taken to the ground on top of the firearm.

Wilcher said that he and his colleague secured the “difficult to control” man’s hands, with the gun going off while he was on top of the man resisting arrest.

“The gun went off while I was on top of this person,” he said.

The AFP denies the terminal was locked down, and would not comment on whether the man reached for the gun at any point or on who was in possession of the firearm when the shots were fired.

The man was approached by officers about 6am following “a report of suspicious behaviour” at the bag check-in counters, AFP acting commander Scott Raven said.

“We allege the man became verbally and physically aggressive towards AFP officers before he was able to be placed under arrest,” Raven said.

“During his arrest, an AFP firearm was unintentionally discharged.

“The circumstances of how the firearm, which was a short-barrelled rifle, was discharged is now subject to an internal investigation.

“Thankfully, there were no injuries as a result of the incident.

“Additional AFP officers assisted with the incident and a crime scene was established and investigations commenced.

“A current and a retired NSW Police officer were also present and assisted with the incident.

“We can confirm that the terminal was not locked down as the incident was contained quickly thanks to our fast actions of our officers.”

A 41-year-old Victorian man known to authorities was arrested at the terminal.

Raven said there is “no ongoing threat to the community” and that there is “zero tolerance” for anti-social, violent or dangerous behaviour at airports.

“Any passenger who breaks the law by being violent or disruptive will be dealt with swiftly,” he said.

Sydney Airport said it is assisting the AFP, adding: “The airport is operating normally.”

The 41-year-old has since been charged with obstructing and hindering a Commonwealth official, and creating a disturbance at an airport.

He has been granted bail to appear in court at a later date.