The riot in manzanar was caused by;

A December 1942 incident at the Manzanar camp that resulted in the institution of martial law at the camp and that culminated with soldiers firing into a crowd of inmates, killing two and injuring many. The incident was triggered by the beating of Japanese American Citizens League leader Fred Tayama upon his return from a meeting in Salt Lake City and the arrest and detention of Harry Ueno for the beating.