Video shows aftermath of Taliban massacre of Pakistan students

On Tuesday, Taliban gunmen massacred more than a hundred children in Peshawar, Pakistan. Witnesses say some of the female teachers were burned alive.

Taliban militants in Afghanistan called the attack "un-Islamic," and now video has emerged offering a look inside the school, reports CBS News correspondent Clarissa Ward.

Pakistan's prime minister, Nawaz Sharif, has lifted a moratorium on the death penalty as three more staff members died from their injuries. In schools across the country, children have gathered, praying together for those who lost their lives.

As families continued to bury their dead, three days of mourning began.

Terrorist attacks are all too common in Pakistan, but few have been quite as deadly or as brutal as this one. Almost all of those killed in Tuesday's eight-hour siege were students. One young boy who escaped described the attack.

"Suddenly there was gunfire behind us," he said. "Some kids were killed, and I was shot in the back."

Other students said they hid under desks as their classmates were picked off around them.

The attack began at around 10 a.m. At least seven men stormed into the military-run school, opening fire indiscriminately on teachers and students with guns and grenades.

Soon after, Pakistani army commandos arrived on the scene. Gunfire and explosions were heard from inside. The militants had planted bombs throughout the school.

When it was over, more than 140 people were dead, leaving a nation reeling.

Taliban militants says deadly siege on Pakistan school was revenge

"What did we do wrong?" a schoolboy from Peshawar asked. "We are not from the army or the Taliban, but they killed small kids."

The Pakistani Taliban claimed the attack was revenge for ongoing military operations in Northern Waziristan that have targeted their hideouts near the Afghan border. By the army's own count, those operations have claimed more than 1,000 lives.