I believe this is who you were thinking of. He was a Coast Guardsman. He is the only Coast Guardsman to ever be awarded the Medal of Honor.
Douglas Albert Munro - Wikipedia
At Lunga Point, the landing craft were instructed to return and extract the besieged Marines.[23] Commander Dexter asked Munro and Evans if they would take charge of the mission, to which Munro answered, "Hell yes!"[4]:4[23] As the boats under Munro's charge approached the recovery points, they came under heavy fire from Japanese forces at a ridge abandoned by the Marines. Munro used a .30 caliber machine gun aboard his landing craft to direct suppressing fire against the Japanese positions as the other boats recovered the American forces. With Japanese troops moving against the beach, Munro piloted his boat closer to shore to act as a shield. Though the initial extraction was successful, one of the LCTs became grounded on a sandbar. Munro directed the other LCT to help extricate the grounded vessel as he maneuvered his own boat to shield the Marines from Japanese fire from the shore. Munro was shot in the base of his skull and lost consciousness.[4]:4
The LCT was ultimately freed and the boats resumed their withdrawal. When out of range of Japanese forces, Munro briefly regained consciousness before succumbing to his wounds. According to Evans, his dying words were, "Did they get off?"[4]:4–5[9] Evans said later that "... seeing my affirmative nod, he smiled with that smile I knew and liked so well, and then he was gone".[23]