At 09.24 hours on 29 April 1943, U-258 fired torpedoes at convoy ONS-5 and reported hits on three ships. However, only one torpedo hit the McKeesport (Master Oscar John Lohr), the other torpedoes detonated away from convoy after missing the ship, which had been in station #42 but had fallen slightly astern. The torpedo struck on the starboard side at the collision bulkhead and the #1 hold. The explosion blew out all beams, hatches and ballast, put the steering gear out of order and opened a large hole. The ship continued at full speed for 45 minutes, but developed a list of 20° to port and began to sink further by the head. Then the twelve officers, 31 crewmen and 25 armed guards (the ship was armed with one 4in and nine 20mm guns) abandoned ship in four lifeboats. Due to the list, they had difficulties to launch the boats, some of them became tangled in the lifenets. The survivors were picked up within 30 minutes by HMS Northern Gem (FY 194) (A/Skipper Lt W.C. King, RNR) and landed on 8 May at St. Johns, but one men died of exposure on the vessel.

HMS Tay (K 232) (LtCdr R.E. Sherwood, RNR) was ordered to sink the ship by gunfire, but apparently the vessel stayed afloat and was sunk by two coups de grâce from U-258 at 14.55 hours.