At around 15:30, approximately ten minutes apart, two grenades were detonated by the militants against security forces outside the school, setting a police car on fire and injuring one officer, but Russian forces did not return fire. As the day and night wore on, the combination of stress and sleep deprivation—and possibly drug withdrawal—made the hostage-takers increasingly hysterical and unpredictable. The crying of the children irritated them, and on several occasions crying children and their mothers were threatened with being shot if they would not stop crying. Russian authorities claimed that the hostage-takers had "listened to German heavy metal group Rammstein on personal stereos during the siege to keep themselves edgy and fired up" (Rammstein had previously come under fire following the Columbine High School massacre, and again in 2007 after the Jokela High School shooting).