A teenager who boarded a commercial flight in Australia armed with a shotgun and ammunition was overpowered by passengers and crew, the police said on Friday.

The teenager, a 17-year-old boy whose identity was not released, had entered the aircraft with the firearm, the department said. Officers from the Victoria Police were called to Avalon Airport in southeastern Australia at about 2:20 p.m. local time on Thursday, it said. He was arrested and faced multiple charges.

A sheep shearer, Barry Clark, was among those onboard the flight who stepped in to detain the teenager. Mr. Clark said that he was headed to Sydney to watch a football match when he noticed a member of the crew asking the teenager, who was dressed in a high-visibility vest and was wearing a tool belt, for his credentials before entering the plane.

“He got agitated and before we know it there was a gun, a shotgun appeared,” Mr. Clark told ABC Radio Melbourne.

“I then proceeded to do what I had to do and just put him in a bit of a lock, got his hand and twisted it and put it up in his back, threw him to the floor and then put my knee in his back and held him in a position where he couldn’t get out,” Mr. Clark told Network 10, a television network, according to The Associated Press.

Police said that they found two bags and a vehicle belonging to the teenager and called in the bomb response unit to assist with the bags as a precaution. No one was injured, they said.

Jetstar Flight 610 was scheduled to fly to Sydney with about 150 passengers. The superintendent of the Victoria Police, Michael Reid, told reporters that the boy had climbed through a hole in the airport’s security fence and made his way to the stairs of the aircraft.

The teenager, from the regional city of Ballarat in Victoria, about 70 miles west of Melbourne, is in custody on eight charges, including unlawfully taking control of an aircraft; endangering the safety of an aircraft; possessing dangerous goods on an aircraft; a bomb hoax; and firearms possession.

On Friday, he appeared in the Children’s Court of Victoria and told the magistrate that he was not applying for bail, according to the Australian broadcaster ABC News. The news report cited charging documents stating that he planted a fake homemade explosive and threatened passengers and crew.

“I’ve got bombs in my bag,” he was quoted as saying.

Mr. Clark, the shearer, said he did not hesitate to get involved, saying that he had been taught as a boy to look after other people. “You don’t think, you act,” he said. “I was quietly confident I could handle him.”

He did not answer the radio interviewer’s question about what was easier, wrangling an attacker or a sheep. Instead, Mr. Clark spoke about the employee who told him seat 1-C was “the best seat in the house” when he made his booking.

Next time, Mr. Clark said, “I am going to ask him if I can go down to cargo.”