What made Gandhiji call off the non-cooperation movement?

As the Non-Cooperation Movement turned violent in some places Gandhiji called off the movement. The main incidence that made Gandhiji call off the movement was Chauri Chaura incidence. Here the peasants set fire to a police station and 22 policemen died. The setting of the police station was in retaliation to the police firing at a peaceful demonstration by the peasants.