At 17.00 hours on 6 April 1942, U-571 fired a spread of two torpedoes at the unescorted Koll (Master Einar Knudsen) east of Cape Hatteras and hit her with both torpedoes on the port side. The explosions killed two men on watch below and set the ship on fire. After 33 survivors abandoned ship in three lifeboats, the U-boat came alongside the boats and asked the usual questions and handed the survivors some crackers. Whereupon the U-boat fired 30 rounds of 8.8cm gunfire into the #1 tank, which exploded and caused the ship to sink at 17.15 hours, while burning gasoline spread across the water with a tremendous development of smoke and heat. A Canadian crew member on a raft took his clothes off when the flames approached and managed to swim away and was picked up after 30 minutes by one of the boats.
The master´s motor lifeboat tried to tow the two other boats, but due to a strong wind the next day, the boats were let go and they lost sight of them after three hours. The survivors in the motor lifeboat were picked up by the Portugese steam merchant Cunene and taken to Lisbon on 25 April.

In the evening on 7 April, the other two lifeboats came across a lifeboat from Kollskegg, which had been sunk by U-754 (Oestermann) that day, but because of heavy seas and a strong wind and rain they could not get close enough to carry on a proper conversation with the survivors in it and they soon lost sight of them. The following day the two boats became separated, because the weather was bad and they constantly had to bail and it was biting cold. On 14 April, the weather improved and the ten survivors in one of the boats could set sail, but in the morning on the next day a light was spotted in the horizon so they sent up rockets. These were seen by the Swiss steam merchant St. Cergue and the survivors were picked up and landed in New York on 17 April.
One crew member in the other lifeboat died of exposure on 14 April, but the remaining nine survivors, one of them badly burned, were picked up two days later by the Portuguese steam merchant Lobito and landed at Lewes, Delaware on 17 April.