It began like any other morning in Pakistan’s Army Public School in the north-western city of Peshawar. Students pored over their books. Teachers ruffled through notes and gave lectures.

Armed men opened fire on Shiite Muslim worshippers during a religious procession in a city in southwestern Pakistan today, killing at least 41 people and wounding more than 150 others.

Authorities have ordered an investigation into the weekend bombing at a ruling party political rally in which at least 22 people were killed.