Nobel Peace Prize winner Malala Yousafzai condemned the attack by Taliban militants on a Peshawar school Tuesday that left at least 126 dead, most of them children. Yousafzai, whose own experience being shot by a Taliban gunman on a school bus in 2012 propelled her to international renown, said she was heartbroken by the tragedy, seen as one of the worst attacks ever on a school in Pakistan, according to the BBC.

"I am heartbroken by this senseless and cold-blooded act of terror in Peshawar that is unfolding before us. Innocent children in their school have no place in horror such as this,” the 17-year-old Pakistani activist said in a statement, according to India Today. “I condemn these atrocious and cowardly acts and stand united with the government and armed forces of Pakistan, whose efforts so far to address this horrific event are commendable."

Pakistani government forces have said that around 500 students were evacuated from the army-run school in Peshawar. Militants stormed the building early Monday morning as students were taking exams and shot at children and teachers, killing at least 100 children, according to a Pakistani provincial official. Army commandos later arrived at the scene and at least five Taliban fighters were believed to have been killed, at least one reportedly in a suicide blast. The Pakistani Taliban later claimed responsibility for the attack, saying it had been planned in response to recent army operations.

Militant violence has been responsible for the deaths of thousands in Pakistan in recent years, but the Peshawar killings have caused unprecedented shock in the country, the BBC reported. Prime Minister Nawaz Sharif, who arrived in Peshawar on Monday, called the attack a “national tragedy.” Indian Prime Minister Narendra Modi called the attack "a senseless act of unspeakable brutality," and offered his condolences to the families of the victims. A number of prominent Pakistani politicians who had previously hesitated to back the army campaign against the Taliban have also added their voices to the condemnation of the attack, which the BBC noted has uncharacteristically united politicians and the army.