Sen. Lindsey Graham, R-S.C., has died at the age of 71 after what his office described as a "brief and sudden illness."
According to NBC News, Graham's office confirmed he died Saturday night and released a statement early Sunday announcing his passing.
The longtime South Carolina lawmaker had served in the U.S. Senate since 2003 and was a close political ally of President Donald Trump.
"Senator Graham's family appreciates prayers at this time and asks for privacy during this incredibly difficult period," the statement said.
Graham was serving as chairman of the Senate Budget Committee and had been seeking a fifth six-year term in the Senate ahead of November's election.
Over more than two decades in Congress, he became one of the Republican Party's most recognizable lawmakers, particularly on defense and foreign policy issues.
According to police scanner audio obtained by NBC News, emergency personnel responded to Graham's Capitol Hill home Saturday night after receiving a report of a person in cardiac arrest.
Photographs reviewed by NBC News showed paramedics carrying an individual on a stretcher from the residence to a waiting ambulance. Police and fire department vehicles were also present at the scene.
Just one day before his death, Graham had been in Kyiv, Ukraine, where he met with Ukrainian President Volodymyr Zelenskyy. He had also been scheduled to appear Sunday on NBC's "Meet the Press."
Graham's death comes during another period of concern for Senate Republicans as Sen. Mitch McConnell remains hospitalized following a separate medical emergency last month.
McConnell was hospitalized after emergency responders answered a call involving an individual experiencing cardiac arrest at a residence.
His office has said the Kentucky senator continues to recover but has not released additional information about his condition or when he may return to Capitol Hill.
With Graham's passing, the Senate loses one of its longest-serving Republican members and a lawmaker who played a prominent role in shaping the party's positions on national security and international affairs throughout his career.
His death also creates an unexpected vacancy in South Carolina as leaders and colleagues begin mourning the loss of the veteran senator.