He then established that the elephant was in musth, a period of behavioural change in the animal usually characterised by aggression, but continued to track it until they were around 50 to 100 metres away.
The elephant then “instantly turned and began a full charge” towards the pair before Mr Gibson was brutally stamped to death.
News of the death was announced online by website Safari Classics, who posted the following message: “It is with deep sadness to announce the passing of Chifuti Safaris professional hunter Ian Gibson.
It continued: “The bull instantly turned and began a full charge. Ian and Robert began shouting in order to stop the charge.
“At very close range, Ian was able to get off one shot before the bull killed him. The scene was very graphic.”
It has been reported that the client was unharmed in the incident.
The story led to fierce debate on the AfricaHunting forum, with the morality of hunting wild animals sparking a row among users.
Earlier this week a female huntress sparked outrage after she posed with a dead giraffe.
Bow and arrow hunter Rebecca Francis was sent death threats after the picture, showing her smiling next to the deceased animal, went viral.
But she has since defended her actions – claiming it was killed so a community could feast on it.