O'Donnell tweeted the news this morning, and shortly after Bungie responded on its blog. Community Manager David Dague said the studio and O'Donnell parted ways "as friends."
"For more than a decade, Marty O'Donnell filled our worlds with unforgettable sounds and soundtracks, and left an indelible mark on our fans," wrote Dague. "Today, as friends, we say goodbye. We know that wherever his journey takes him, he will always have a bright and hopeful future. We wish him luck in all his future endeavors."
We've reached out to Bungie for further details.
O'Donnell's departure is certainly a surprise given his stock with Halo and Bungie fans, especially with Destiny rapidly approaching its release date of September 9. The veteran composer had collaborated with former Beatle Paul McCartney on a "musical prequel" to Destiny, titled Music of the Spheres. It has yet to be released.
Update: Speaking to a group of journalists at a studio event (keep your eyes on Joystiq for Destiny preview coverage soon), Bungie COO Pete Parsons made the following statement. "I'm sure many of you have heard the news about Marty O'Donnell. At Bungie, we don't take that kind of thing lightly. We don't make decisions lightly. We're a team that's committed to making an amazing game, set in an amazing universe." He added, "At this time, we won't be commenting any further on it."