Dave is retiring...

Of course, Dave prerecords his show, which left time for word to leak before it aired...so who really broke the news?

...it was ex-R.E.M. bassist Mike Mills.

Mills and ex-R.E.M. guitarist Peter Buck were performing on Thursday night's episode of the Late Show as part of Joseph Arthur's band. And after Letterman made his announcement to the audience, Mills tweeted "Dave just announced his retirement #2015 #muchlovedave." The news spread quickly after his tweet as the media attempted to confirm the story.

Late Show producers interviewed Mills after the show, and when asked why he tweeted out the news