At 22.06 hours on 9 March 1943 the Puerto Rican (Master Ralph Albert Oliver) was hit by one torpedo from U-586 about 100 miles northeast of Iceland. The ship was straggling from convoy RA-53 since two days due to heavy weather and was at the time of the attack about 25 miles behind convoy. The torpedo struck on the starboard side aft of the #5 hatch and caused the ship to sink on even keel in 15 minutes. The eight officers, 32 crewmen and 25 armed guards (the ship was armed with one 5in, one 3in, four 20mm, four .50cal and two .30cal guns) tried to abandon ship in the four lifeboats and the rafts in rough seas and 30° below zero weather. They only managed to launch one boat because the others were frozen in their chocks. This boat capsized when the after fall failed to release and all occupants fell into the sea, where most of them quickly froze to death in the 21° water.

Eight men eventually swam to a doughnut raft and six later transferred to a large provisioned raft. In the following two days all these men except one froze to death or washed off the raft. The sole survivor, the fireman August Wallenhaupt wearing a lifesaving suit, was picked up on 12 March by HMS St. Elstan (FY 240) (Lt R.M. Roberts, RNR) and landed in Seydisfjordur, Iceland. From there he was taken to a hospital in Reykjavik aboard the American troop transport USS Gemini (AP 75), arriving on 16 March. He eventually lost both feet and most of the fingers of both hands.