The plan was executed on the evening of 27 June 1908, when the group of Vietnamese cooks managed to mix datura poison with food they had prepared for a party. The poison immediately knocked out nearly 200 French troops but did not kill them. Moreover, one of the cooks had felt guilty and had gone to a church for confession, the French priest then reporting this to government officials; the French general-in-charge in Hanoi immediately proclaimed martial law and ordered the arrest of plot leaders and plotters. Outside the citadel, Hoang Hoa Tham did not receive the signal he was expecting, realized the plot had failed and withdrew all his troops.