The artillery exchange between the PRT/MEB and US happens on June 21st around midnight, when the MEB start shelling fort shad from their tree base. A shot will be fired and the music will play, along with a distant air raid siren. Two buildings in Southside will be blown to bits (The Soupshark and Post office) along with some areas in the forest, a Howitzer-Anti-Aircraft in Fort Wilmington, and half of the bridge on the PRT side. The reason for the US firing on pieces of land all over is because they thought they were taking fire from Southside when they were not. On the radio next morning, (June 22, 2115) It is reported there was a loud BANG in the forest before the Artillery-fire started, which was the MEB starting their raid on Fort Shad from their tree base/bunker in the woods.
Note: This server event has now been removed due to the calender system ingame being removed, however LPMs can load in this event