At 13.55 hours on 29 June 1942 the unescorted Thomas McKean (Master Mellin Edwin Respess) was hit by two torpedoes from U-505 about 350 miles northeast of Puerto Rico, while steaming on a zigzag course at 10 knots on her maiden voyage. The torpedo struck aft of the #5 hold, destroyed the stern gun and killed three armed guards. Due to the extensive damage, the eight officers, 31 crewmen, 17 armed guards (the ship was armed with one 4in, four 20mm and two .30cal guns) and four passengers abandoned ship in four lifeboats. The U-boat surfaced after 20 minutes and began shelling the ship with 72 rounds that set her on fire until she sank at 15.22 hours. The Germans questioned the survivors and some crewmen even boarded the lifeboats to administer first aid treatment before they left the area.

One crewman and one armed guard later died in the lifeboats. On 4 July, two boats with 29 survivors made landfall at St. Thomas, Virgin Islands and one boat with twelve survivors landed at Antigua on 12 July. On 14 July, the last boat with 14 survivors and one dead arrived at Micheson, Dominican Republic. The master was lost during repatriation as a passenger on Onondaga which was sunk by U-129 (Witt) on 23 July.