"These are very experienced elephant hunters," he said.
The slaughter comes at a time when the world's leaders are meeting to address this very problem. In Botswana, the Africa Elephant Summit has gathered leaders from more than 20 countries, including the world's largest ivory market, China.
New numbers released there by the International Union for Conservation of Nature don't give much hope for the African elephant population, which dropped from 550,000 in 2006 to 470,000 in 2013.
Dune Ives, a U.S. researcher, gave the leaders a dire warning about the future of elephants.
"This species could be extinct in our lifetime, within one or two decades, if the current trend continues," he said.