I know that after they gained power residents of Phnom Penh were forced from their homes to be incorporated into Pol Pot's agrarian-based utopia. But what happened to the country's capital during this period? Was it essentially a ghost city, being completely devoid of people, or were there some who were exempt from the forced exodus imposed by the khmer rouge?
One great book to read is "First They Killed My Father". Also try "Brother Number One". In short though the Khmer Rouge pretty much did empty the city of people and transplanted them to the country side. People with any amount of education were usually targeted for elimination as their education had "tainted" them with western thinking.
Phnom Penh was used by the new government as a base of operations. S-21 detention center in Phnom Penh was where they kept detainees for torture and "re-education". Those living in the city were higher up members of the Communist Party, some essential industry was kept in place in the city, but for the most part it became just a military zone and government headquarters.