Walter Palmer has said he "deeply regrets" killing the 13-year-old lion, who was found shot, skinned and decapitated beyond the safety of the Hwange National Park, where he had been a drawcard for tourists.
The apology has fallen flat on Twitter where the hashtag #WalterPalmer is being used to hurl insults and threats at the dentist, who allegedly paiod at least $50,000 to hunt and kill the animal.