Complex sentence: When the Trailways bus reached Anniston and pulled in at the terminal an hour after the Greyhound bus was burned, it was boarded by eight Klansmen, who proceeded to beat the Freedom Riders and afterwards left them semi-conscious in the back of the bus.
Split into simpler sentences: When the Trailways bus reached Anniston and pulled in at the terminal an hour after the Greyhound bus was burned, it was boarded by eight Klansmen. They beat the Freedom Riders and left them semi-conscious in the back of the bus.