Which is CORRECT about the exchange of gunfire?

North Korean and South Korean military units exchanged gunfire near their border Friday, South Korean authorities said.
    No casualties were reported. The exchange happened after North Korean forces fired two rounds from a 14.5 millimeter machine gun at a South Korean military guard post near the border town of Chorwon, South Korea, about 73 miles northeast of Seoul, according to an official at the Joint Chiefs of Staff. The South Korean unit responded with three "warning shots" from a 50-caliber machine gun and warned the North Korean guard post by loudspeaker to desist, the official said.
    Chorwon was the scene of heavy fighting during the 1950—1953 Korean War. North Korea on Friday threatened to retaliate against its neighbor for shunning bilateral military talks. The gunfire exchange apparently won’t cancel reunions of families separated by the Korean War, which ended in a truce but no formal peace treaty. (24) The weeklong reunions begin Saturday at Mount Kumgang, the two countries’ joint mountain resort in the North.