At 05.47 hours on 14 May 1942 the unescorted David McKelvy (Master Carl A. Zwicker) was hit by one torpedo from U-506 about 35 miles south of the mouth of the Mississippi River, as she proceeded on a zigzag course at 10 knots. The torpedo struck amidships on the port side at about the #4 tank. A huge explosion set the ship on fire and the water around the tanker quickly became covered with burning oil. The U-boat surfaced, Würdemann examined the vessel and decided to leave without to do further damage. The master and the three deck officers perished as the bridge crumpled in the flames. 23 men among the eight officers, 28 men and six armed guards (the ship was armed with one 4in and two .50cal guns) abandoned ship 20 minutes after the hit in the #3 lifeboat. Some others jumped overboard and swam to two rafts. These survivors were picked up by USCGC Boutwell (WPC 130) and taken to the section base at Burwood, Louisiana. Four were badly burned and were taken to the Marine Hospital in New Orleans, where one crewman died. The Chief Engineer and the pumpman survived by standing in the fresh water tanks of the ship´s double bottom until the fire burned out. The two men were picked up by the Norwegian motor tanker Norsol the next day and taken to Key West, Florida. Four officers, 11 men and two armed guard died.

A salvage crew reboarded the burned out tanker on 29 May and prepared to tow her to the beach. After beaching on the coast of Louisiana, she was declared a total loss.