Rep. Tom Cole announced Monday the death of his longtime chief of staff, Sean Murphy.

The Oklahoma Republican put out a statement saying Murphy died suddenly of natural causes.

“He was a wise counselor, a good friend and a generous mentor to dozens of people who have worked in my congressional office and my political campaigns. He will be missed by all who knew him, but especially me,” the congressman said. 

Murphy is survived by his wife and three children.

He worked as Cole’s chief of staff for over 11 years and previously as chief of staff for four years to former Colorado Republican Rep. Bob Beauprez.

Murphy, a Colorado native, began his career as a congressional aide in Fort Collins, working on a 1996 and 1998 campaign. He was the executive director of the Colorado Republican Party from 1999 to 2002 before working for Beauprez.

He graduated with a political science degree from the University of Colorado Boulder in 1989.