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By Mushtaq Yusufzai and Fazul Rahim

A U.S. drone strike in eastern Afghanistan on Saturday killed the mastermind behind the 2014 attack on a military-run school in Pakistan that left more than 130 children dead, the Pakistani military said.

Khalifa Omar Mansour, a top commander of the Pakistani Taliban, died in the strike, Taliban sources also confirmed, adding that three of his bodyguards were believed dead.

Mansour, 37, had been in the Nangarhar province along the Pakistani border when the strike occurred.

Taliban commander Umar Mansour in a video posted by the banned militant group.Pakistan Defence

The death of Mansour was announced on the Pakistani military's social media pages, which said he also went by the aliases Umar Narai, Khalifa Umar and Khalid Khurasani.

He was also physically frail, and family members nicknamed him "Naray," or slim.

A U.S.-led coalition forces spokesman confirmed that a counterterrorism strike occurred Saturday, but would not discuss the details.

Related: NBC News Visits the Scene of Taliban Attack

Mansour is accused of coordinating the carnage on Dec. 16, 2014, at the Army Public School in Peshawar. The attack left 132 schoolchildren, from ages 8 to 18, dead, along with nearly a dozen teachers — making it one of the deadliest on Pakistan soil.

The Pakistan Taliban claimed responsibility. Pakistan officials said the attackers, who disguised themselves in police uniforms and wore suicide vests, appeared to be targeting the children of senior military personnel.

Mansour later said the Peshawar attack was to seek ‎revenge of a Pakistan forces operation against the Pakistani Taliban in the tribal areas along the Afghan border.

The Peshawar school shooting was followed on Jan. 20 by another attack on students, this time at Bacha Khan University in Charsadda. More than 20 people were killed and another 20 were injured.

Initially, Mansour spoke with NBC News via telephone and took responsibility for the Charsadda siege.

"This is a reaction to extrajudicial killing of our people by the Pakistani security agencies," Mansour said at the time.

He also issued video statements proudly claiming to have organized both the Charsadda and Peshawar attacks.

He said the Bacha Khan University killings were against students who could eventually become part of the army and judiciary to work against the Taliban.

Erik Ortiz contributed.