Photographer Christophe Courteau was taking images of mountain gorillas in Rwanda's Volcanoes National Park forest when the group's alpha male charged him.

Courteau is a pro: he got the shot of that incoming fist before the punch hit him.

The ape was reportedly "drunk" from eating bamboo stems, which ferment in the stomachs of gorillas. Basically, their bodies make their own beer.

"In less than a second, he was on me, and strongly hit me like a rugby player. With the shock, I felt all his power and weight on my body," Courteau told Caters News Agency.

"I was taking photos of the gorilla family on the slopes of the Virunga Mountains with several clients of mine," said Corteau. "We were all mostly focusing on a silverback called Akarevuro, the leader of the Kwitonda Group.

"All the members of this family were quite excited on this day, probably due to the consumption of the bamboo stems, which cause the gorillas to become extremely drunk and excitable.

"Suddenly, Akarevuro, who was stood close to us, just ran at me, but I could not move away as I was taking photos on my knees.

"In less than a second, he was on me, and strongly hit me like a rugby player.

"With the shock, I felt all his power and weight on my body.

"A silverback gorilla like him weights around 250kg, so imagine a 250kg rugby player running straight towards you. Normally, they timidly avoid visitors when they move close, but not this time, Akarevuro was too excited and drunk.

"He did not care about me, and pushed me out the way with his left hand like if I was not there.

"Then he dashed through the vegetation to chase away a black back male behind us who looked to be interested in one of Akarevuro's females."

More images here.