US Fish and Wildlife Service unable to contact Minneapolis dentist about Cecil the lion's death

The U.S. Fish and Wildlife Service has not been able to contact the American dentist accused of killing a beloved lion in Zimbabwe, agency director Dan Ashe said on Thursday.

Ashe, in a post on Twitter, called the killing of Cecil the lion "tragic" and said his agency will "go where facts lead" in its investigation of the lion's death.

Suburban Minneapolis dentist Walter Palmer has admitted to killing the animal but said he believed the hunt was legal.