Kosovo marks a day of mourning after a deadly weekend clash between authorities and gunmen near the Serbian border left one police officer dead and another wounded. The officer was killed when a police patrol was ambushed near the northern village of Banjska, a predominantly Serb area, early on Sunday. The perpetrators then fled to a nearby monastery, where they traded gunfire with Kosovo police for hours. At least four assailants were killed in the melee. The incident marks one of the gravest escalations in Kosovo for years and comes after months of mounting tensions between Pristina and Serbia. "I was very scared," says one resident of Kosovo's capital, "it's terrifying." IMAGES AND SOUNDBITES