McCasky
From Halopedia, the Halo wiki
Second Lieutenant McCasky was a ommanding officer on the ground during the Battle of Sigma Octanus IV. He and his squad were sent on a scouting mission when he and most of his Marines were killed by the fuel rod gun of a Hunter.
Four of his unit did survive though, Corporal Harland, Private Fincher, Private Walker, and Private Cochran.