A man who had been sending letter bombs to German officials all year blew himself up this week to escape a DNA test. Johann Lang, 22, an unemployed loner, was found dead in a field, his corpse badly burned. Police found bomb-making equipment and prototypes littering Langs room in the isolated farmhouse where he lived with his father and aunt. But authorities gave no motive that could explain why Lang sent nine crude letter bombs, only one of which caused injury, to Bavarian officials in the Passau region. The reason for his suicide was clearer: Police had found the bombers DNA on one of the letters and scheduled mass DNA tests for all men in Passau.