The Taliban attack on a Pakistan school on Tuesday that left more than 140 dead was motivated by the militant group's war with Pakistan's army, NBC News reported. "The Taliban could have attacked any one of the thousands of schools across the country," said retired Maj. Gen. Mahmud Ali Durrani. "They deliberately went after the children of the soldiers they're fighting." The militants attacked the military-run school in Peshawar, killing at least 132 children and 10 staff members, a military spokesman said. Pakistani military sources said six Taliban militants were killed at the scene. The attackers were wearing police uniforms and suicide vests, a military source told NBC News. About 500 students and teachers were believed to be inside Army Public School at the time of the attack. "The gunmen entered class by class and shot some kids one by one," a student who was in the school at the time told local media. The U.S. condemned the attack, calling it "senseless and inhumane."