Nobel Peace Prize winner Malala Yousafzai condemned Tuesday's attack in a school in northwest Pakistan, saying she and her family were "heartbroken". Gunmen from the Pakistani Taliban stormed a military-run school in Peshawar on Tuesday, killing at least 141 people, mostly children, before Pakistani officials declared a military operation to clear the school over. The violence has underscored the vulnerability of Pakistani schools, which was dramatically exposed in the attack two years ago on Yousafzai, a Pakistani girl shot in the head by a Taliban gunman outside her school in the Swat Valley for daring to speak up about girls' rights. She survived, becoming a Nobel Prize laureate in 2014 and a global advocate for girls' education. Out of security concerns, she has never returned to Pakistan.