It is said that the criminal was SUGAWARA no Tamenaga or anti-Kujo group who were bitter about the relationship between Yoshitsune and the Kamakura bakufu (Japanese feudal government headed by a shogun).
犯人は菅原為長とも、良経の鎌倉幕府との関係を苦々しく思った反九条派の仕業とも言われているが、定かではない。