Watch David Letterman Make It Official: He's Retiring Next Year

'The network has been great. But I'm retiring,' Letterman said during Thursday night's show.

Perhaps you expected him to make his big announcement by writing it on a turkey and tossing it off the roof? Or spelling it out in Alka-Seltzer and dipping himself into a huge pool of water?

Nope. When it came time to confirm reports that he was retiring

after a highly influential three-decade run in late night television, David Letterman shocked his studio audience by being uncharacteristically sentimental.

He kicked off Thursday's monologue with some spring baseball, court stenographer, allergy and Chris Christie jokes like it was just another night in the trenches. But when he sat down after the first commercial break, the man who changed the face of late night television forever dropped his bombshell.

Letterman, the longest-running host in U.S. late night TV history, prefaced the news by noting that he will soon turn 67, figuring that he's spent half his life making us laugh from behind his desk. "More importantly, that means I've spent half my life in makeup," he joked of his 4,014 shows at CBS and another 1,810 at NBC.

The news came as part of a cute story about a recent fishing trip with his 10-year-old son, Harry, in which Harry took a striking picture of a rare immature bald eagle, which Letterman spent a whole day trying to identify. "If you spend most of you day trying to I.D. birds, should you really be running a network television program?" he asked. What was his point? Life is short.

Top 10 Reactions To David Letterman's Retirement Announcement

"The man who owns this network, Leslie Moonves, he and I have had a relationship for years and years and years, and we have had this conversation in the past, and we agreed that we would work together on this circumstance and the timing of this circumstance," Letterman said. "And I phoned him just before the program, and I said 'Leslie, it's been great, you've been great, and the network has been great, but I'm retiring.'"

The audience reacted with stunned silence, while longtime sidekick Paul Shaffer asked if he could have a moment to call his accountant.

"I just want to reiterate my thanks for the support from the network, all of the people who have worked here, all of the people in the theater, all the people on the staff, everybody at home, thank you very much," Letterman added.

The news was actually broken by former R.E.M. bassist Mike Mills, who was on the program that night to perform with singer Joseph Arthur.

Not sure when exactly he'll hang it up, Letterman said the last show will be sometime in 2015, as the audience jumped to its feet to give him a standing ovation. Later in the broadcast, guest Johnny Depp informed Dave that he had a "lot of weepers" backstage following the announcement.

"I myself was on the verge," Depp said. "It was only because I had planned to announce my retirement here. And now that's ruined because no one cares."