The John A. Treutlen (Master Gustav Anderson) was struck by one torpedo on the port side between the #5 hold and the after peak tank and blew a large hole in the side. The explosion lifted the stern out of the water and flames and water shot into the air. It forced its way forward and set off the after magazine. This second explosion blew another huge hole in the port side. The blast broke the shaft, destroyed the steering gear and cracked the vessel athwartships, leaving the stern hanging several feet lower. The most of the eight officers, 35 crewmen and 31 armed guards (the ship was armed with one 5in, one 3in and eight 20mm guns) abandoned ship in three lifeboats, leaving only a skeleton crew of twelve men and the master on board. The survivors, ten of them injured (nine armed guards and one crewman) were picked up by HMCS Buctouche (K 179)(SkrLt H.E. Young, RCNR) and the American landing ship USS LST-336 and taken to Southampton on 30 June.
The next morning, the tug WSA-2 arrived and towed the vessel to Southampton, where she was beached. The cargo was salved and the vessel declared a total loss.

The John A. Treutlen was on her maiden voyage and had loaded cargo at Savannah and Jacksonville, Florida. She proceeded to New York and left on 5 May, en route to the Clyde in convoy HX-290 arriving in Scotland on 19 May.