According to "Shinsengumi Shimatsuki" by Kanefuji NISHIMURA (a samurai serving at Nishi Honganji-Temple where Shinsen-gumi placed their military post), the assassins were HIJIKATA, OKITA, YAMANAMI and HARADA.
西村兼文（新選組が屯所を置いた西本願寺の寺侍）の『新撰組始末記』では実行者は土方、沖田、山南、原田になっている。