At 06.36 hours on 27 February 1942 the unescorted R.P. Resor (Master Frederick Marcus) was hit by one torpedo from U-578 about 20 miles east of Manasquan Inlet, New Jersey, while steaming blacked out on a zigzag course at 12.5 knots. The torpedo struck on the port side just forward of amidships and blew oil over the entire length of the ship and into the water. The oil ignited and flames rapidly spread 500 feet around the tanker as the eight officers, 33 crewmen and nine armed guards (the ship was armed with one 4in gun) tried to abandon ship. One boat with about 30 occupants was launched successfully but was soon engulfed in flames, other men perished as they tried to swim through the oil. One crewman and one armed guard were picked up by the picket boat USCGC CG-4344 and landed at the Manasquan US Coast Guard station.

The burning tanker stayed afloat until the tug USS Sagamore (AT 20) attempted to salvage her. She capsized after the stern grounded in 122 feet of water and sank almost 48 hours after the torpedo hit about 31 miles east of Barnegat, New Jersey.