Assailants wearing masks attacked the office of an aid group in a rugged Pakistani town, killing two people and setting five vehicles on fire at the compound before fleeing, police said Sunday. The shooting at the office of Aga Khan Foundation occurred late Saturday in Chitral, an isolated town about 250 kilometers northwest of the capital Islamabad. Four men, whose faces were covered, opened fire with assault rifles on the network's office, killing two of its workers - a security guard and a driver, who both were locals. Before disappearing into the darkness, the attackers torched five pickup trucks in the compound, he said. No one claimed responsibility and the police official said authorities were investigating a motive for the attack. The office in Chitral of the Aga Khan Foundation, an internationally known aid group ran by the spiritual head of Ismaili Muslims in Pakistan, supervised health clinics that it operated in Chitral, which is also name of the mountainous district. Chitral is located along the border with Afghanistan where Pakistani officials have denied that Osama bin Laden is hiding.