The principal of the army-run school that was attacked by Pakistani Taliban gunmen in Peshawar has been confirmed dead by Pakistan Army spokesperson Asim Bajwa during a media briefing in Peshawar on Tuesday evening.

Referring to the terrorist attack that has claimed at least 141 lives, including 132 children and nine staff members, as a 'Black Day', Bajwa announced the loss of Tahira Qazi, the school's principal.

Bajwa said it appears the terrorists did not intend on creating a hostage situation since they fired off indiscriminately at groups of schoolchildren after entering the school's auditorium from the back, which was the less guarded entrance.

An estimated 1,099 students and staff members were reportedly registered at the army-run school and the army's Quick Response Force (QRF) that acted within 15 minutes of the attack, rescued 960, said Bajwa.

The seven Taliban militants were eventually cornered off to the administration block and shot down by security forces.

"We know who they are and who they were in contact with but details can not be share[d] due to operation reasons. They were aware of locations... it is highly possible that someone from inside might have tipped them off," said Bajwa.

The school has now been handed back to its administration after demolition of all the recovered ammunition left behind by the militants.

Bajwa confirmed that several general threats had followed since the start of Pakistan Army's Operation Zarb-e-Azb, however the army-run school was never specifically mentioned.

Operation Zarb-e-Azb was launched by the Pakistan Army on 15 June in North Waziristan against militant groups, including the Tehrik-i-Taliban Pakistan (TTP), Lashkar-e-Jhangvi, Jundallah, al-Qaeda, as well as the Haqqani network.

The Pakistani Taliban, Tehrik-i-Taliban Pakistan (TTP), has so far claimed responsibility for Tuesday's attack as a revenge against the army offensive, Operation Zarb-e-Azb, in north Waziristan.

"We selected the army's school for the attack because the government is targeting our families and females. We want them to feel the pain," said Muhammad Umar Khorasani, spokesman for the militant group.