A 92-year-old Japanese survivor of the U.S. atomic bombing of Nagasaki described the horrors he witnessed in 1945 as he accepted this year’s Nobel Peace Prize on Tuesday on behalf of his anti-nuclear weapons group.

Terumi Tanaka, a survivor of the U.S. atomic bombings of Japan and the representative of an organization that won this year’s Nobel Peace Prize, has called on Russian President Vladimir Putin to stop making nuclear threats.