OWINGS MILLS, Md. -- Kevin Kamenetz, a Democratic candidate for governor of Maryland and Baltimore County Executive who was a fixture in state politics for nearly 25 years, has died. Kamenetz died early Thursday, following a cardiac arrest, Baltimore County police said in a news release. He was 60.

The two-term county executive was at home in Owings Mills when he awoke around 2 a.m., complaining of feeling ill, according to the release. He was hospitalized at St. Joseph Medical Center, where he was declared dead at 3:22 a.m.

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 a former president of the Maryland Association of Counties and the Baltimore Metropolitan Council.

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He attended Johns Hopkins University and the University of Baltimore School of Law. He is survived by his wife, Jill Kamenetz, and two teenage sons.

Kamenetz was one of seven candidates vying for the Democratic nomination to oppose Republican Gov. Larry Hogan this fall. The Democratic primary is scheduled for June 26. He had chosen Montgomery County Councilmember Valerie Ervin as his running mate.

"I can't even believe this happened," Ervin told The Baltimore Sun early Thursday.

Kamenetz campaign spokesman Sean Naron echoed that sense of shock.

"We really don't know how to put it into words," he told the Sun. "Right now, we're focused on the fact he was the father to two teenaged sons."

Longtime aide and chief of staff Don Mohler had known Kamenetz for two decades.

"I am just sitting in my office numb," the Sun quoted him as saying.

Condolences from political leaders began rolling in after the news broke Thursday morning.

Current Governor Larry Hogan tweeted that he is shocked and grieved by the death of Kamenetz and sends his prayers to his family.

The First Lady and I are shocked and grieved by the sudden passing of Baltimore County Executive Kevin Kamenetz. Our prayers go out to his family and many loved ones this morning. — Governor Larry Hogan (@GovLarryHogan) May 10, 2018

Another Democratic candidate for governor, Ben Jealous, released a statement that commended Kamenetz for helping "to move Maryland forward." In a tweet, he remarked on how the dictates of alphabetical seating meant the two candidates were often placed next to one another at forums, and remembered Kamenetz's "grace and good humor."

Another rival candidate, Alec Ross, said he was "shocked and saddened."

Kamenetz's campaign touted his track record with education and the environment, highlighting a historic $1.3 billion investment in public education and the renovation or construction of 90 schools. His campaign website says the adoption of innovative education policies helped raise the public school graduation rate to nearly 90 percent, while eliminating the graduation gap between black and white students. He described himself as an environmental advocate who spearheaded initiatives to safeguard the Chesapeake Bay and reduce the county's carbon footprint.

His campaign website positioned him as a contrast to President Donald Trump, whom he criticized for attacks on immigrant communities. He also emphasized his fiscal policies, which resulted in no tax increases or government furloughs or layoffs during the Great Recession.

Kamenetz sometimes came under fire for a style that critics described as impatient. On the campaign trail, he embraced his brusque personality, saying public service demands urgency and he's "always been the person who will look you in the eye and tell you the truth."

It's yet unclear how Kamenetz's sudden passing will affect the calculus of the primary race and general election. As for Baltimore County, administrative officer Fred Homan will serve as acting county executive until the council votes on a replacement to serve the remainder of his term. The seat is also up for grabs this fall.

CBS Baltimore reports that officials say Baltimore County Administrative Officer Fred Homan will take over Kamenetz's position until the County Council can vote on an Acting Executive to serve the remainder of the term.