Unknown gunmen shot dead an American aid worker and his local driver in Pakistan's volatile northwest on Wednesday, officials and police said. The attack occurred in University Town, an upscale area of the main northwest city of Peshawar where a top US diplomat was attacked just a few months ago, police official Arshad Khan said. US Embassy acting spokesman Wes Robertson declined to identify the American or say what he was doing in the area other than to say he was not a diplomat. However, a Western security official in Peshawar said the slain American worked for a development organization with projects in the northwest. The security official spoke on condition of anonymity because he is not authorized to speak to media.