Kevin Kamenetz, considered to be one of the leading Democratic contenders for governor in Maryland, died early Thursday morning of cardiac arrest, police have said.

Kamenetz, the Baltimore County executive, woke at about 2 a.m. and said he was not feeling well, Baltimore County police said. He was taken to St. Joseph hospital and died soon after, police said. Kamenetz was 60 years old.

Maryland Gov. Larry Hogan and his wife expressed their sympathies to Kamenetz’s loved ones in a statement. He ordered the state’s flags to be lowered in his honor.

“He was a dedicated public servant in Baltimore County for more than two decades, and we join with the citizens of Baltimore County and all Marylanders in mourning,” Hogan, a Republican, said. “In the difficult days to come, we will provide any support we possibly can to the Kamenetz family and the citizens of Baltimore County.”

Valerie Ervin, a Montgomery County councilmember, was Kamenetz’s running mate. She told The Baltimore Sun that she couldn’t believe the news.

Don Mohler, his longtime aide, told the newspaper that he was “just sitting in my office numb,” after he learned.

After beginning his public service career as a prosecutor in the Baltimore City State’s Attorney’s Office, he was elected in 1994 to the Baltimore County Council, where he served four terms. He was also a former president of the Maryland Association of Counties and the Baltimore Metropolitan Council.

During the gubernatorial campaign, Kamenetz emphasized his fiscal policies, which resulted in no tax increases or government furloughs or layoffs during the Great Recession -- while he was in office. According to The Sun, Kamenetz was able to renovate schools and downtown Towson during his time in office without a tax increase.

One of his campaign pledges, according to the newspaper, was to “look you in the eye and tell you the truth.”

As one of seven candidates vying for the Democratic nomination to oppose Hogan in the fall, Kamenetz positioned himself as a foil to President Trump, whom he criticized for his attacks on immigrant communities. The Democratic primary is scheduled for June 26.

On Twitter, Ben Jealous, another Democratic candidate, said he would be seated next to Kamenetz during most forums because it was arranged alphabetically.

“I’ll always remember him for the grace and good humor he showed each of his fellow candidates as we lined up backstage waiting … for the event to begin,” Jealous said. He also noted that Kamenetz “dedicated his life to public service, to making a difference” and helping the state move forward.

Kamenetz was consistently in the top three of the field of Democratic candidates in polling and raised more money than anyone else so far, The Baltimore Sun reported. He also recently blocked more than $1 million worth of airtime in the Baltimore and Washington, D.C., areas.

“His absence will shake up the race because he was an important political figure in the state,” Mileah Kromer, a Goucher College political science professor, told the newspaper. “He had a serious record for any candidate to run on. That, of course, is a loss. That is a loss to the Democratic Party and a loss to the voters of Maryland.”

According to his campaign website, Kamenetz attended Johns Hopkins University and the University of Baltimore School of Law. He grew up with five older siblings. As The Sun reported, Kamenetz often talked about his upbringing as the son of a pharmacist in Lochearn, Maryland, just outside of Baltimore, and the lessons he learned from his father when he ran the cash register at the store.

Kamenetz leaves behind his wife, Jill, and two teenage sons.

For now, administrative officer Fred Homan will serve as acting county executive until the council can vote on a replacement to serve until the fall, which would have been the remainder of Kamenetz’s term.

The Associated Press contributed to this report.