President Barack Obama has condemned a Taliban attack on a Pakistani school that killed at least 126 people, mostly children and teenagers.

“By targeting students and teachers in this heinous attack, terrorists have once again shown their depravity,” Obama said in a statement Tuesday.

The president called the attack “horrific” and said he condemns it “in the strongest possible terms.”

The Taliban’s siege on the Army Public School in Peshawar, Pakistan, began early Tuesday morning when armed gunmen stormed the school. The overwhelming majority of fatality victims were students at the school, according to The Associated Press. The Taliban said the attack was revenge for the deaths of Taliban members caused by Pakistani authorities.

The AP reports that approximately nine militants had been killed.

“We stand with the people of Pakistan, and reiterate the commitment of the United States to support the Government of Pakistan in its efforts to combat terrorism and extremism and to promote peace and stability in the region,” Obama said.