From Halopedia, the Halo wiki
Matt Soell was an employee at Bungie Studios, from 1995 to 2003. He worked on Marathon, Myth, and Halo: Combat Evolved. He also was the voice of Crewman 1 in Halo: Combat Evolved. During the production of Halo 1, he posted a series of updates as to how the game was coming along called Matt's Bungie Update. When Bungie began work on Halo 2, this torch was taken up by Frank O'Connor. In Halo, the Soell System and the Soellkraft 8 Gauge Shell are named after him.
April 25, 2003 was his last day at Bungie and he released this statement:
He now works at Certain Affinity.