Video shot in June but going viral this week shows a dramatic encounter between a large male kangaroo and a man in Australia.

The man, who was reportedly out pig hunting with his dog and several friends in rural New South Wales, saw that his hunting dog was being forced into a headlock by a large kangaroo. The man, reported to be Greig Tonkins, 34, rushed up to help his dog.

Startled, the kangaroo let go of the dog. But Tonkins—who told media that he wanted to scare off the kangaroo and give his dog a chance to retreat—punched the marsupial in the face.

"The guy's very lucky because he could have been killed," says Marco Festa-Bianchet, a National Geographic explorer who studies kangaroos and who is a biologist at Université de Sherbrooke in Quebec.

Contrary to popular belief, kangaroos don't normally try to box, or punch, each other, says Festa-Bianchet. Instead, they prefer to balance on their strong tails and kick with their powerful back legs.

"If the kangaroo had done that to the guy it could have disemboweled him," says Festa-Bianchet.

Watch: Kangaroo vs. Kangaroo

Another technique kangaroos sometimes use is to try to claw their opponents' eyes out, which also could have left Tonkins seriously injured.

The kangaroo is clearly a large male, Festa-Bianchet says. It stands roughly 6 feet tall and may weigh as much as 170 pounds. An animal like that could be 9 to 15 years old and is in the prime of its life.

Male kangaroos often battle each other in the wild over access to breeding females, sometimes to the point of death. Usually, however, a male will yield to the stronger challenger, often showing subservience by grooming or making a coughing sound.

"I’m sure the punch hurt," says Festa-Bianchet. "You can tell the kangaroo is like, 'Whoa what was that?' That’s not what another kangaroo would do and a human does not give the right signals. It kind of looks funny but it really was a dangerous situation."

After taking the hit, the animal retreated into the bush—without visible injury, Tonkins reported.

Did Tonkins Act Improperly?

Internet commenters have expressed outrage over the punch, with some asking why Tonkins didn't simply retreat as soon as the kangaroo let go of his dog. But Festa-Bianchet cautions against too much armchair analysis.

"The guy was obviously hyped up and had to make a split decision," he says. "He clearly felt threatened by the animal and wanted to save his dog."

"Still, I would advise against doing that," he adds.

National Geographic has been unable to reach Tonkins for comment. Exactly what precipitated the fight between the dog and marsupial is unclear, although Festa-Bianchet says kangaroos are used to contending with dingoes, which often prey on them.

"Kangaroos often defend themselves by wrestling the dogs to the ground, which is what you can see happening in the video," he says.

Tonkins actually works in the wildlife industry and serves as a zookeeper on the staff of the Taronga Western Plains Zoo, the zoo confirms in a statement. The zoo says they are investigating the incident.

Tonkins's employment is not in jeopardy, the statement says. In his six years on the job, Tonkins "has always followed Taronga’s best practice approach to animal care and welfare," the zoo notes. "However, the highest standards of animal welfare and care are a core value of Taronga and one that we expect our staff to uphold in all their interactions with wildlife."

"Taronga strongly opposes the striking of animals and does not support the practice of using dogs to hunt, as this can result in negative welfare for both species," the zoo writes.

Friends of Tonkins have spoken out in support of his actions, saying he did what the situation called for in protecting himself, his dog, and his friends. The purpose of the trip was to help a sick friend hunt a boar, they say. That man has since died from his illness.

Hunting of the invasive boars—which have caused ecological damage in Australia—is popular there. In some cases, hunters use dogs to subdue the pigs and then finish them off with knives, never touching a gun.