JOHANNESBURG -- A male lion known to wildlife lovers around the world as Cecil has been illegally killed by a party of game hunters, according to the Zimbabwean government.

The Zimbabwe National Parks and Wildlife Authority and the Safari Operators Association said two men, one a landowner whose property is adjacent to a game reserve, and the other a professional big game hunting guide, were facing poaching charges.

It's believed the professional guide lured the big cat named Cecil into moving out of the safe confines of Zimbabwe's Hwange Game Reserve so that it could be killed by the foreign hunter, identified by conservation groups including the Zimbabwe Conservation Task Force, as American Walter James Palmer, whose history of big game hunting is documented online.

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On Tuesday, Palmer released a statement saying that to his knowledge, "everything about this trip was legal and properly handled and conducted."

"I had no idea that the lion I took was a known, local favorite, was collared and part of a study until the end of the hunt. I relied on the expertise of my local professional guides to ensure a legal hunt," he said. "I deeply regret that my pursuit of an activity I love and practice responsibly and legally resulted in the taking of this lion."

Palmer added that he had not been contacted by authorities in Zimbabwe or in the U.S. but promised to cooperate if they had questions.

But African wildlife expert Dex Kotze says it is impossible that Palmer's hunting team didn't know it was Cecil.

"I mean a black mane lion like that you can see from afar and even on a hunt. You are definitely going to identify that this -- hang on this is a collared lion and it is Cecil. Because all the conservationists and wildlife industry in that area would have been very familiar with that lion Cecil," Kotze told CBS News' Debora Patta.

In Zimbabwe Debora Patta reached Brent Stapelkamp. He's part of the Oxford scientific team that has collared and tracked Cecil.

American dentist, Walter James Palmer, accused of killing beloved lion Cecil. The lion in this photo is another lion, not Cecil. CBS News

"He's come in here to shoot a lion, a national emblem and he's been caught. So I would hope he gets everything that justice throws at him," Stapelkamp said.

Cecil was no ordinary lion -- he had been tagged by the Wildlife Unit of Oxford University in the U.K. and was the subject of over a decade of research. It appears he was shot with a bow and arrow and then stalked for more than 40 hours before being finished off with a rifle shot.

Speaking to CBS News in a Skype interview, the founder of the research unit at Oxford, Prof. David MacDonald, said it appeared Cecil was lured across the border by freshly slaughtered animal bait into a neighboring hunting concession area.

"Our understanding is that when he was shot by a bow hunter outside the park he was shot illegally," MacDonald told CBS News. "If so, that is unforgivable and a terrible tragedy for lion conservation."

"Cecil" the lion walks through Zimbabwe's Hwange Game Reserve in an undated file image. Brent Stapelkamp

The once proud alpha male lion was found beheaded and skinned. And there are fears that Cecil's death could lead to many more. As Animal Planet's predator expert David Salmoni explained to CBS News, Cecil had six cubs who will now probably be killed by a male lion from another group or coalition, as they are known.

"If one lion is shot from the coalition, it weakens the coalition and results not just in the death of that one lion, but the death, probably, of his companions, because the weakened coalition will be overtaken by the stronger coalition which in turn will kill the cubs of their predecessors," Salmoni said. "So it may well be that the death of just one lion leads to the deaths of several more, and for a species that is declining fast, that is very bad news."

Zimbabwe's Professional Hunting Association is investigating the incident but has claimed it was a private safari and therefore not illegal.

The Zimbabwean government disagrees, however, and arrested the hunting guide and land owner who were allegedly involved in the incident. Those men were to appear in court Wednesday, according to officials.

Palmer allegedly paid $55,000 to join the hunt during which Cecil was killed.

People involved in the game hunting industry in Africa argue that money paid for legal hunts is ploughed back into wildlife conservation. But critics argue the same amount of money could be made through tourists visiting game reserves to see magnificent animals like Cecil roaming free in their natural environment.