Article Photos: 21 missing Pakistani policemen found shot dead 3/3

EDS NOTE: GRAPHIC CONTENT - Pakistani volunteers help a critically injured passenger on his way to a hospital following a blast in Karachi, Pakistan on Saturday, Dec. 29, 2012. The blast that ripped through the bus  set the vehicle on fire and reduced it to little more than a charred skeleton, killing scores of people and left many injured. Police were trying to determine whether the explosion was caused by a bomb or a gas cylinder, said police spokesman. Many buses in Pakistan run on natural gas. (AP Photo/Fareed Khan)