Apparently of a heart attack at age 58. Details as they emerge at Hot Air.

Brent Bozell, whom Allahpundit notes in the link above is--understatement alert--no fan of the MSM writes:

Whenever I’ve been asked to give examples of a fair, balanced and honest journalist Tim Russert’s name was the first name that came to mind. This was a view shared by everyone and the ultimate testimony to his professionalism. As a moderator he was in a league of his own, always knowing when to speak and when to let his guests do the talking. As an individual he was an absolute class act, and always a gentleman. The world of journalism is vastly diminished today.

A truly class act indeed, the likes of which are now in that much shorter supply at NBC and its affiliated cable networks.

Update: Statement from President Bush:

Laura and I are deeply saddened by the sudden passing of Tim Russert. Those of us who knew and worked with Tim, his many friends, and the millions of Americans who loyally followed his career on the air will all miss him.

As the longest-serving host of the longest-running program in the history of television, he was an institution in both news and politics for more than two decades. Tim was a tough and hardworking newsman. He was always well-informed and thorough in his interviews. And he was as gregarious off the set as he was prepared on it.

Most important, Tim was a proud son and father, and Laura and I offer our deepest sympathies to his wife Maureen, his son Luke, and the entire Russert family. We will keep them in our prayers.

Russert frequently--and jovially--interviewed Rush Limbaugh, particularly at Thanksgiving, demonstrating himself to be one of the few in the MSM comfortable with those across the aisle.

Update: Speaking of being comfortable with the other side, Russert even once all-too-briefly donned a Fox News blazer.