At 07.50 hours on 13 Aug 1942 the unescorted R.M. Parker Jr. (Master Walter Ord Peters) was hit on the port side amidships at tanks #5 and #6 by two torpedoes from U-171 about 25 miles south of Isles Dernieres, Louisiana. Lookouts had spotted the wakes but too late to alarm the bridge. The explosions toppled the mainmast, buckled the decks and opened a large hole that flooded the tanks and caused a severe list. The engines were secured, a distress signal sent and the ship turned to starboard to cut the speed, while the armed guards had to leave the guns due to the heavy list. The eight officers, 29 crewmen and seven armed guards (the ship was armed with one 5in and two .50cal guns) abandoned ship in three lifeboats.
The U-boat then surfaced off the starboard quarter and fired five rounds from the deck gun into the tanker. The first shell caused the ammunition in the ready box for the stern gun to explode and the others struck the midship house and the bridge. The tanker sank by the stern until she rested on the bottom with her bow above the water and a 25° list to port. After eight hours she finally disappeared.
The survivors were picked up eight hours after the attack by the US Coast Guard auxiliary craft USS Pioneer and landed the same day at Morgan City, Louisiana.