Former Sen. Kay Hagan has died at 66, after complications from a prolonged illness

Former U.S. Sen. Kay Hagan, D-N.C., died on Monday in her home in Greensboro, North Carolina, according to her family. She was 66.

"We are heartbroken to share that Kay left us unexpectedly this morning," the family said in a statement. "Kay meant everything to us, and we were honored to share her with the people of North Carolina whom she cared for and fought for so passionately as an elected official."

Hagan is survived by her husband, Chip, and her three children, Tilden, Jeanette and Carrie.

In 2016, Hagan contracted a brain inflammation from a tick-borne virus. Hagan was hospitalized in Atlanta for about six months before beginning outpatient treatment, according to the Greensboro News & Record.

Hagan served a single term from 2009 to 2015, after defeating Republican Sen. Elizabeth Dole in 2008. Hagan lost her reelection campaign to Republican Sen. Thom Tillis in 2014, in what was then the most expensive Senate race ever.

Tillis said in a tweet that he and his wife, Susan, were "heartbroken."

Before working in politics, Hagan worked as an attorney and eventually became vice president of what is now Bank of America.

She began her political career as a county campaign manager for former North Carolina Gov. Jim Hunt's campaigns in 1992 and 1996. She was recruited in 1998 to run for a state Senate seat, representing a Greensboro district, where she served for five terms after unseating a Republican incumbent.

When she ran for the U.S. Senate, Hagan won 60% of the vote in the Democratic primary, and was aided by having Barack Obama's name on the ballot in the general election.

The former president, in a statement Monday afternoon, called Hagan a "terrific public servant."

"She was, quite simply, a terrific public servant -- eager to find common ground, willing to rise above the partisan fray, and always focused on making progress for the people she served," he said in the statement.

Hagan spent her term focusing on the passage of the Affordable Care Act and the Dodd-Frank bill, which overhauled banking regulations, calling it, "commonsense Wall Street reform so American taxpayers will never again have to shoulder the cost of a financial crisis."

"As President, I deeply appreciated her reasoned, pragmatic voice, whether we were working together to pass the Affordable Care Act, reform Wall Street, support working families, or just make Americans' lives a little better," Obama said in the statement. "Her record is one all public servants would do well to follow, and her perspective is one we'll sorely miss."

After she was unseated, she became a resident fellow at the Harvard Institute of Politics.

According to the News & Record, Hagan made a rare public appearance in June, at the groundbreaking ceremony for an air traffic control tower, a project she helped advance during her time in the Senate. Her husband, Chip, told the paper that she had limited physical and speech capabilities, but was working "very hard to improve the situation."

Former Vice President Joe Biden said in a statement that he and his wife, Jill, are "deeply saddened" at the news of her death.

"Kay Hagan was a courageous soul who lived every day of her too-short life with incredible dignity and character, even as the days became more difficult physically," Biden said in the statement on Monday. "I am grateful that I had the opportunity to see her in person just yesterday during my visit to Durham, and to spend time privately with her and Chip. She was a champion for North Carolina and a fierce defender of all its citizens."

Hagan came from a political family.

She was born in Shelby, North Carolina, and her family moved to Florida, where her father ran a tire sales business and later served as the mayor of Lakeland. Her uncle, Lawton Chiles, served as a U.S. senator and Florida governor.

After attending Florida State University and earning a bachelor's degree in American Studies, Hagan spent six months in Washington interning for her uncle and operating a senators-only elevator.

In 1975, Hagan graduated with a law degree from Wake Forest University before working in the trust division of North Carolina National Bank, now Bank of America.

North Carolina Democratic Gov. Roy Cooper ordered flags to be lowered to half-staff to honor the life and service of Hagan to North Carolina.

"Kay was a fierce advocate for North Carolina, and she represented our state with courage and grace her entire career. She made it a mission to inspire young people -- especially young girls -- to enter public service, and she served as a role model to so many," Cooper said in a statement. "North Carolina is mourning one of our best today."