The FBI is assisting local authorities following the sudden death of Republican Sen. Lindsey Graham, one of Washington’s most influential foreign-policy voices and among Israel’s strongest supporters in Congress.

Graham’s office announced that the South Carolina senator died after a “brief and sudden illness,” but officials have not released a confirmed cause of death. FBI Director Kash Patel said the bureau had made every necessary resource available, while giving no indication that investigators suspect foul play.

Emergency responders were called to Graham’s Capitol Hill home at approximately 8:30 p.m. after receiving a report that someone inside was suffering from chest pains. Dispatch audio later indicated that Graham had gone into cardiac arrest and that CPR was underway before he was transported to George Washington University Hospital. His death was announced several hours later.

Cardiac arrest describes the moment the heart stops functioning, but authorities have not publicly identified what caused it. The FBI’s assistance has fueled intense online speculation because of Graham’s high-profile international role, though no evidence has emerged connecting his death to a foreign government or any outside actor.

President Donald Trump said Graham called him at approximately 7 p.m., less than two hours before emergency services were dispatched. Graham had just returned from Ukraine and sounded “a little tired, but perfect,” according to the president. Trump described Graham as being like a member of his family and ordered American flags nationwide lowered to half-staff in his honor.

Graham had been photographed in Kyiv shortly before his death, meeting Ukrainian President Volodymyr Zelenskyy and visiting military facilities. It was his 10th trip to Ukraine since Russia launched its full-scale invasion, and he had just announced progress on a new package of sanctions targeting Moscow.

The timing of his death also drew attention to the threats Graham faced from the Iranian regime. Days earlier, mourners at Supreme Leader Ali Khamenei’s funeral carried placards showing Graham and other prominent American and pro-Israel figures with red crosshairs over their faces. Graham publicly mocked the threat. Iranian state media later celebrated his death, but authorities have announced no evidence linking Tehran to what happened.

For Israel, Graham’s death removes one of the Jewish state’s most committed and outspoken defenders in Washington. He consistently argued that American and Israeli security were inseparable, championed military pressure against Iran and forcefully defended Israel’s right to destroy the Hamas terrorist organization following the October 7 massacre.

Graham served in Congress for more than three decades, entering the House of Representatives in 1995 before joining the Senate in 2003. A former Air Force lawyer who retired from the reserves as a colonel, he became a central figure in debates over Iran, Israel, Ukraine, Russia, national defense and the federal judiciary.