Russert had just returned to work from a family vacation in Italy where he and his wife, journalist Maureen Orth, celebrated the graduation of their son, Luke, from Boston College.

Prior to joining the NBC news organization, Russert served as press secretary for former New York Governor Mario Cuomo and as chief-of-staff to Senator Daniel Moynihan. His career at NBC started in 1984 and he has earned accolades for being the first American broadcaster to negotiate an appearance by Pope John Paul II. He also received an Emmy in 2005 for his coverage of the funeral of President Ronald Reagan. Time Magazine named him one of the 100 most influential people in the world.

Tom Brokaw brought the news live at approximately 3:40 p.m. to NBC viewers.

"This was one of the most important years in Tim's life for so many reasons. He loved this political campaign. He worked to the point of exhaustion so many weeks, not just on `Meet the Press,' but on MSNBC, and with our colleague, Brian Williams, of course, during the debates and on `Special Coverage' on NBC Nightly News."

Colleagues from around the globe have stated their condolences. Jeff Zucker, CEO of NBC Universal released in a statement, "We are heartbroken at the sudden passing of Tim Russert. We have lost a beloved member of our NBC Universal family and the news world has lost one of its finest. The enormity of this loss cannot be overstated. More than a journalist, Tim was a remarkable family man. Our thoughts and prayers are with his wife, Maureen, their son, Luke, and Tim's entire extended family."

Others weighed in, highlighting the mentoring they had received from Russert. Andrea Mitchell said during a broadcast today, "Tim was our friend, our leader, our cheerleader, our teacher, my mentor. Tim came to this bureau in 1988, 20 years ago, as the bureau chief. Even before that, he, of course, was a vice president of NBC News and was in charge of the `Today' program and a great contributor to shaping political coverage. He was a guide to all things political.

Editor's Note: It has since been reported that Mr. Russert's death was caused by plaque that "ruptured an artery, causing a sudden coronary thrombosis." Source: NBC