Starting on May 19, 1999, NATO forces bombed the town of Istok, killing three prisoners and a prison guard that day. Two days later, NATO forces struck the prison complex again, with at least 19 prisoners being killed from the airstrikes, according to Human Rights Watch. Subsequent to the lethal airstrikes, special units from the Yugoslavia's Ministry of Internal Affairs along with various criminals selected by the special forces carried out a false flag operation, during which the prisoners were massacred by firearms, after which state agency Tanjug claimed that all of the prison victims were killed by the airstrikes.