Complex sentence: Shortly after completing the work, Schulz was bringing home a loaf of bread when he was shot and killed by a German officer, Karl Günther, a rival of Landau, who had killed Günther's "personal Jew", a dentist.
Split into simpler sentences: Shortly after completing the work, Schulz was bringing home a loaf of bread when he was shot and killed by a German officer, Karl Günther. Günther was a rival of Landau, who had killed Günther's "personal Jew", a dentist.