Brian Morden
From Halopedia, the Halo wiki
Brian Morden aka Ar-Isildur was neither an actor nor an employee at Bungie Studios, but he contributed to Halo: Combat Evolved as an additional voice actor. Born January 10, 1984 in Altoona, Pennsylvania, USA, Morden contributed to Halo: Combat Evolved at the age of only sixteen. It was to be his only screen credit. He voiced the Marine who yelled out, "The Autumn, she's been hit!" in the "Pillar of Autumn Final" Cutscene.[1]
Brian Morden died suddenly on February 15, 2003 at the age of nineteen of a condition called Ewing's sarcoma.[2]
Morden's name appears on the ONI memorial in Halo 3: ODST as both an Easter egg and a tribute.
He is referenced twice in Halo: Reach. "B. Morden" is mentioned in the halo.bungie.org terminal in the Tribute Room as a "known associate" along with Claude Errera and Miguel Chavez. One of the human troops recruitable via the Fireteam mechanic is also named B. Morden.
