A tourist has captured the moment a silverback gorilla took a swipe at three people in his group in Rwanda.
The huge animal charges past two tourists and their guide before grabbing one of them and pushing him to the floor.
Their group had been watching the animals feed when the incident occurred.
"The slope was very steep and we were all trying to get a view of the family as they were feeding.
"The silverback decided that he wanted to get to the other side of the guests and gave a mock charge."
The Sun reports that he added: "The guests lost their footing and started to roll down the hill.
"The guide grabbed the one guest and they went tumbling down with the silverback chasing after them.
"It grabbed the guide's arm, as he still held onto the guest and the gorilla calmed and carried on eating as the two of them slipped out from under the gorilla's nose."
The mountain gorilla is one of the two subspecies of the eastern gorilla.
There are two populations. One is found in the Virunga volcanic mountains of Central Africa, within three National Parks: Mgahinga, in south-west Uganda; Volcanoes, in north-west Rwanda; and Virunga in the eastern Democratic Republic of Congo (DRC).
It is listed as critically endangered by the IUCN.
The other is found in Uganda's Bwindi Impenetrable National Park.
As of September 2016, the estimated number of mountain gorillas remaining is about 880.