At 11.39 hours on 3 Nov 1942, U-521 fired a spread of three torpedoes at convoy SC-107 about 400 miles south of Cape Farewell and hit the Hahira in station #81 (the ship had been in station #82, but the leading ship had been torpedoed earlier) with one torpedo. Bargsten thought that he had also hit another ship of 4000 tons, but this is not confirmed by Allied reports.

Lookouts on the Hahira (Master James Bronna Elliott) spotted a torpedo track pass ten yards ahead of the ship and another pass off the stern. The third torpedo struck on the starboard side in the #9 tank. The explosion virtually blew the after part away and sprayed blazing fuel oil over this part of the vessel. The fire suppressant system managed to put out most of the fire, allowing the crew to abandon ship. Five minutes after the hit, the complement of eight officers, 30 crewmen and 18 armed guards (the ship was armed with one 4in, one 3in, four 20mm and two .30cal guns) began leaving the ship in three lifeboats and one raft. All men got away, except two crewmen and one armed guard. The survivors were picked up 45 minutes later by the British rescue ship Stockport and landed in Reykjavik on 8 November. The wreck of the Hahira was later sunk by U-521 with two coups de grâce at 15.18 and 15.22 hours, after an attempt to scuttle the tanker by gunfire by one of the escorts failed.

14 of the survivors were being repatriated on the Parismina, when she was torpedoed and sunk by U-624 (Soden-Fraunhofen) on 18 Nov 1942. Three men from the Hahira were lost.