Former Oklahoma Sen. James Inhofe died Tuesday at the age of 89, Fox News has confirmed.

Inhofe, a Republican, was the state's longest serving senator from 1994 to 2023 and passed away peacefully this morning surrounded by his wife Kay, his children and other family members, a former senior aide tells Fox News.

Inhofe, the aide said, had come down with a sudden and unexpected illness around the Fourth of July holiday.

Further details were not immediately available.

James Mountain Inhofe started serving Congress in Washington in 1987 in the House of Representatives before being elected to the Senate in 1994. At one point, he was the top Republican on the Senate Armed Services Committee. 

Prior to his time in Washington, Inhofe served as the mayor in his hometown of Tulsa, Oklahoma, between 1978 and 1984, according to the Oklahoma Historical Society. He also served in the U.S. Army in 1955-56 and was president of the Quaker Life Insurance Company before entering politics, it added. 

Rep. Kevin Hern, R-Okla., described Inhofe on Tuesday as a "dear friend and mentor, a titan in Oklahoma, and a highly effective leader in D.C."

"Tammy and I are keeping Kay and the rest of the Inhofe family in our prayers," Hern said in a statement. "Jim spent his life in service to his country, both in uniform and in the halls of Congress. He will always be remembered as a fighter, especially for our military service members."

This is a developing story. Please check back for updates.

Fox News' Chad Pergram and Marisa Schultz contributed to this report.