At 07.22 hours on 15 March 1942 the unescorted and unarmed Ario (Master Thorolf R. Hannevig) was 11 miles southwest of the Cape Lookout Buoy and had to change her course, because a small vessel crossed the port bow. So the tanker was not steering a zigzag course, when she was struck three minutes later by a torpedo from U-158 on the starboard side at #9 tank. The radio operator sent a distress signal and received an answer. The master ordered the ship abandoned, but before any of the boats could be launched the U-boat opened fire at the vessel. For 30 minutes the ship was shelled with 40 rounds, while the crew of eight officers and 26 crewmen cleared the ship. The #3 boat containing 12 men was struck by a shell before it reached the water, killing five men, while two others were picked up by another lifeboat but died of injuries and one man died later in hospital. U-158 closed in to view the vessel and almost collided with a lifeboat before leaving the area.
Later the master, the chief mate, the second mate, the chief engineer and an able seaman reboarded the Ario to check for possible salvage, but the vessel was in sinking condition. After seven hours the survivors were picked up by the USS Du Pont (DD 152) and landed at Charleston. One officer and seven men died in the attack.

The Ario was still afloat when last seen at 18.30 hours on 15 March. She finally sank in shallow water about 10 miles east of Cape Lookout in 34°14N/76°27W.