Complex sentence: Williams initially told them that they were free to go, but he soon realized that the crowd would not grant safe passage; therefore, the white couple was lodged until later that night in a house nearby until they were able to safely leave the neighborhood.
Split into simpler sentences: Williams initially told them that they were free to go, but he soon realized that the crowd would not grant safe passage. He kept the white couple in a house nearby until they were able to safely leave the neighborhood.