At 23.03 hours on 10 June 1940 the Mount Hymettus was stopped by U-101, which had chased the ship since 18.00 hours and the master was ordered to come to the U-boat with the papers. At 00.30 hours, Frauenheim spotted another U-boat and was not sure about its identity, dived when he observed that the unknown U-boat dived and fired a torpedo at the steamer, but it understeered the target. The other U-boat was U-43 (Ambrosius).
Frauenheim decided to wait until dawn to sink the steamer, but when he tried to stop the nearest steamer at 06.30 hours the ship did not react and morsed that they don\'t understand his orders. But then Frauenheim noticed that he had tried to stop the American steam merchant Washington, apologized his mistake and wished the ship a good journey.
At 08.30 hours, U-101 found the Mount Hymettus again, ordered the crew to leave the ship and transferred the master into one of the lifeboats. At 11.17 hours, the U-boat hit the ship with one torpedo in the stern, but it remained afloat and had to be sunk with 78 rounds of gunfire.