Complex sentence: After nine hours or more, a single gunshot sounded from inside the classroom, which caused the Dyersburg police to bust in and open fire, killing Kilpatrick and wounding two students.
Split into simpler sentences: After nine hours or more, a single gunshot sounded from inside the classroom, which caused the Dyersburg police to take action. They forcibly entered the room and opened fire, killing Kilpatrick and wounding two students.