Former Tonight Show host Johnny Carson, 79, died Sunday morning, a relative informed AP.
No cause of death was given, but Carson had emphysema and had lately had trouble breathing, according to a friend.
Still, the death was not expected by some close to him.
That same friend, Peter Lassally, a former executive producer on Carson's show and now with Letterman, told TV critics last week that Carson was doing "just fine," watching the late-night shows over East Coast feeds from his California home and occasionally feeding jokes to Letterman.
Like many comics, Letterman's career took off when he became a regular on The Tonight Show. He eventually got the slot after Carson and was widely expected to succeed him. Carson's choice of Jay Leno, another frequent guest host, sent Letterman to CBS.
Carson was host of Tonight for three decades before retiring in 1991.
Carson himsellf had taken the guest host route to the center seat, subbing for Jack Parr for three weeks in 1958 to good notices. He replaced Parr Oct. 1, 1962.
Carson brought an extensive TV resume to the job.
Born in Corning. Iowa, Oct. 23, 1925, Carson served in the Navy in the South Pacific, then graduated from the University of Nebraska, Lincoln, in 1948.
After announcing jobs at WOW-AM-TV in Omaha and KNXT Los Angeles, he made his first appearance as a comedian on a national stage in NBC-TV's All-Star Review Dec. 27, 1952.
After a stint as a comedy writer for Red Skelton, he got a gig as host of CBS game show, Earn Your Vacation, in 1954, followed by evening and daytime versions of comedy/variety show, The Johnny Carson Show, in 1955-56. He hosted the ABC daytime gaem show, Who Do You Trust from 1957 to 1962, when he replaced Parr on the NBC late night show, where he began a thirty-year stint as one of TV's most popular and highest-paid stars.
While the Tonight Show's first seminal host, Steve Allen, was a one man band, with talents to match any guest, and Jack Parr a brilliant and urbane center of attention, Carson was the master of commanding left-center stage, skillfully asserting a comfortable, likeable presence while leaving the spotlight to his guests.
Carson's show became something of a Good Joketelling Seal of Approval for stand-up comics, and Carson's favorite part of his show was the topical stand-up monologue he delivered.
Jerry Seinfeld once said that his appearance on the Carson show was the turning point of his comedy life.
The sign that a comic had made it, or had impressed Carson, was an invitation to sit down after their stand-up.
When asked once what was his favorite part of the Tonight Show, Carson said he couldn't pick one, but that rolling with unscripted moments was a highlight.
Those included numerous run-ins with animals and one oft-cited tomahawk demonstration by singer Ed Ames (then playing an indian character on TV), in which the tomahawk landed on the target in a phallic position. The result was one of the longest unplanned laughs in TV history.
One of the audience's highlights was the penultimate Carson appearance. Bette Midler sang a Carson-tailored version of the Sinatra torch song "One for My Baby" that had the stoic Midwestern Carson dewy eyed and the rest of the audience in two-handkerchief territory.