On 29 April 1932, Yun took a bomb disguised as a water bottle to a celebration arranged by the Imperial Japanese Army (IJA) in honor of Emperor Hirohito's birthday at Hongkew Park, Shanghai (one contemporary news report states Yun threw a hand grenade but they also say he was killed at the scene). The bomb killed the government minister for Japanese residents in Shanghai, , and mortally wounded General Yoshinori Shirakawa, who died of his injuries on 26 May 1932. Among the seriously injured were Lieutenant General Kenkichi Ueda, the commander of the 9th Division of the Imperial Japanese Army, and Mamoru Shigemitsu, Japanese Envoy in Shanghai, who both lost a leg, and IJN Admiral Kichisaburō Nomura who lost an eye. The Japanese Consul-General in Shanghai, , was seriously injured in the head and body.