Walla's reason for departure? He "longs for the unknown" and wants to continue building his music career outside of Death Cab for Cutie - which he's already had success with, having produced for The Decemberists, Tegan & Sara, Nada Surf, and the Postal Service, among others.

"Deciding to leave the band was not, and is not, easy," he wrote. "It's really, really sad. I love my bandmates, and I'm proud of what we've done, and mercifully, those things don't change with my departure. Moving forward, my plans are simply to continue making music, producing records, and erring on the side of benevolence and beauty whenever possible. Darkness may find me, but I shall never choose it."

As for his former bandmates, there's no word on who will replace Walla but they have showed their support for his decision to leave. On their Facebook page, they issued the statement: "We've had an incredible 17 years of making music with Chris. We are very proud of what we've accomplished together, including our eighth studio album which we have just put the finishing touches on. We will miss Chris and wish him all the best in the next chapter of his career. We are excited about sharing new music, and seeing all of you very soon."