Complex sentence: This small group of armed radicals had attacked several congressmen, wounding two in the arm and were fleeing awat when they encountered Touchstone, who was entering the building with three other clerks.
Split into simpler sentences: This small group of armed radicals had attacked several congressmen and wounded two in the arm. The radicals were fleeing when they encountered Touchstone, who was at the time entering the building with three other clerks.