"It was a magnificent, mature lion. We did not know it was well-known lion. I had a licence for my client to shoot a lion with a bow and arrow in the area where it was shot," he said.
The hunter said he reported the "mistake" to the Parks and Wildlife Management Authority the following day.
The client, who is believed to have paid £35,000 for the hunt, has not been identified. There were reports on Sunday that the person was Spanish, but the Zimbabwean hunter identified him to The Telegraph as "North American".
In a statement, the Zimbabwe Professional Hunters and Guides Association (ZPHGA) confirmed that the professional hunter in the group involved in the killing was one of its members and was suspended with immediate effect.
"ZPHGA reiterates that it will not tolerate illegal hunting or other unethical practices by any of its members," the organisation said.
"Hunting at night by spot light should be banned. It is not fair and it is cruel, and the loss of this lion was a tragedy," said Trevor Lane, a veteran Zimbabwe conservationist in Victoria Falls.
Zimbabwean authorities are now searching for the head of Cecil which is expected to become a prized trophy, but they suspect it may already have been taken out of the country.