Washington (CNN) Former Indiana GOP Sen. Richard Lugar died at age 87 early Sunday morning, the Lugar Center in Washington announced.

"His loving wife Char, his four sons Mark, Bob, John, and David and their families were with him throughout his short illness in the hospital," the center's announcement read.

Lugar, a longtime Republican senator and foreign policy leader, served in the Senate from 1977 to 2013. He was unseated in a 2012 primary and went on to helm the Lugar Center, whose work focuses in part on nonproliferation.

"Senator Richard Lugar is a towering figure in Hoosier history and one of the greatest statesmen ever to serve in the U.S. Senate. As our longest serving Senator, he worked tirelessly with leaders across the globe to better the state and the country he loved," Indiana Republican Sen. Mike Braun said in a tweet on Sunday. "Maureen and I are praying for the Lugar family in this difficult time."

Maureen and I are praying for the Lugar family in this difficult time. — Senator Mike Braun (@SenatorBraun) April 28, 2019

Purdue University President and former Indiana Gov. Mitch Daniels, who served for years as Lugar's chief of staff before becoming governor, said in a statement later Sunday that Lugar was "not just the finest public servant I will ever know, he was the finest person."

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