Complex sentence: The desperate Martens then decides to kill his son, but in the meantime, Commissioner Seiler finds out that Engel has committed suicide and that Martens has been fooled.
Split into simpler sentences: The desperate Martens then decides to kill his son but he does not bring this on himself. In the meantime, Commissioner Seiler finds out that Engel has committed suicide and Martens had just been fooled.