JEFFERSON CITY, Mo. (AP) -- Missouri Auditor Tom Schweich, a Republican candidate for governor, died Thursday of a self-inflicted gunshot wound, a staff member told The Associated Press.

The auditor's office staff member spoke on condition of anonymity because the person was not authorized to speak publicly about the cause of death. A statement from Schweich's spokesman confirmed the 54-year-old had died but didn't list a cause.

Schweich was taken to the hospital Thursday after what his staff described as a "medical situation" at his home in the St. Louis suburb of Clayton.

"It is with great sadness that I confirm the passing of Missouri State Auditor Tom Schweich today," spokesman Spence Jackson said in the statement. "Please keep in mind his wife Kathy and two children."

Schweich had served as auditor since January 2011 and won re-election in November to a second, four-year term. He announced a month ago that he was seeking the Republican nomination for governor in 2016, and was gearing up for an expected primary fight against Catherine Hanaway, a former U.S. attorney and Missouri House speaker.

Schweich made his political debut in 2009. He had initially considered running for the seat being vacated in 2010 by Republican U.S. Sen. Kit Bond, and he had the encouragement of his mentor, former U.S. Sen. John Danforth. But Schweich decided to defer to Rep. Roy Blunt to avoid a divisive GOP Senate primary and instead challenged and defeated Democratic State Auditor Susan Montee in the 2010 election.

He previously worked as a private-sector attorney and for the federal government. Schweich was Danforth's chief of staff for the 1999 federal investigation into the deadly government siege at the Branch Davidian compound in Waco, Texas, and followed Danforth to the United Nations, where he was chief of staff for the U.S. delegation.

President George W. Bush appointed Schweich to the State Department in 2005 as an international law enforcement official. Two years later, Bush picked Schweich to coordinate the anti-drug and justice reform efforts in Afghanistan.

In a statement, Missouri Gov. Jay Nixon, a Democrat, called Schweich a "brilliant, devoted and accomplished public servant who dedicated his career to making the world a better place."

In a November interview with The Associated Press, Schweich said he was mulling a run for governor at that time because "a lot of people want to clean up Jefferson City, and I think I would be well-equipped to do that."