NEW : One officer was hurt in a third night of violence in Belfast . NEW : About 150 youths fired shots and threw bombs at officers . NEW : Police are now trying to identify those involved . BELFAST, Northern Ireland (CNN) -- The latest violence began after a decision to allow a Protestant parade to pass through a mainly Catholic neighborhood on July 12 , a day when Protestants march to celebrate the victory of England 's King William III over his ousted Catholic predecessor , James II , in 1689 . Prime Minister David Cameron denounced `` unacceptable '' violence .
NEW : One officer was hurt in a third night of violence in Belfast . NEW : About 150 youths fired shots and threw bombs at officers . NEW : Police are now trying to identify those involved . BELFAST, Northern Ireland (CNN) -- Prime Minister David Cameron denounced `` unacceptable '' violence .