State Rep. Peter Kocot, D-Northampton, addresses a crowd in Pulaski Park during the "Our Lives on the Line" march and rally in Northampton on Saturday, July 29, 2017. The event was part of a national day of action against Republican efforts to repeal or scale back parts of the Affordable Care Act.

Shauneen O'Donnell Kocot and Peter Kocot laugh at a joke at their expense by the guest speakers, Dr. Raymond Conway and Brian Rust the St. Patricks Day breakfast at the Hotel Northampton Thursday morning. CAROL LOLLIS

State Rep. Peter Kocot, left, and Northampton Mayor David Narkewicz were among those attending a protest against white nationalism Sunday outside City Hall in Northampton in the wake of violence in Charlottesville, Va. on Saturday.

NORTHAMPTON — State Rep. Peter V. Kocot, a longtime Northampton Democrat who has served as the 1st Hampshire District’s representative since 2002, died Thursday. He was 61 years old.

Kocot had been battling an illness in recent weeks, according to state Rep. Stephen Kulik, D-Worthington. He is survived by his wife, Shauneen, and his two sons, Jake and Luke.

“I’m sorry to say it’s true,” Kulik said of Kocot’s death. “It’s a huge, huge loss to the region, to his family and friends and to the district. Just a really, really amazing legislator.”

Joseph Kocot, Kocot’s brother, now retired; said Peter, the oldest of five siblings, had assumed the role of head of the family after their parents had passed.

“He’s been the patriarch of the family,” Joseph Kocot said.

He noted how the family was proud of his work at the Statehouse, and how his brother had enjoyed outdoor activities.

No funeral or memorial for Kocot has been planned as of Thursday evening.

Ellen Story represented the 3rd Hampshire District on Beacon Hill from 1992 to early 2017, and knew Kocot as both an aide and a legislator.

“He was one of the savviest legislators in the building,” she said. “And one of the smartest.”

Story characterized Kocot as one of the stars of the legislature, and said he always had the big picture in mind.

“He is irreplaceable,” she said.

At the time of his death, Kocot served as chairman of the Joint Committee on Health Care Financing. He was also a member of the House Committee on Ethics, which he once chaired.

House Speaker Robert DeLeo sent an internal email to lawmakers Thursday informing them of Kocot’s death.

“It is with profound sadness that I write to notify you that our dear friend and colleague, Peter Kocot, passed away this morning,” DeLeo wrote. “Chairman Kocot was one of the most kind, decent, and selfless individuals that I have had the pleasure to know. Our prayers are with Peter’s wife, Shauneen, his children, extended family, and his staff.”

Senate President Harriette Chandler said in a statement she was deeply saddened to learn of Kocot’s death.

“Chairman Kocot was a passionate leader and a strong advocate for his constituents,” she said. “His experience and presence will be deeply missed in the State House.”

U.S. Rep. Jim McGovern, D-Worcester, said in a statement Kocot was a fighter for the less fortunate.

“Peter was a great public servant with a big heart. He fought hard for what he believed in, and always listened carefully to the communities that sent him to Beacon Hill,” McGovern said.

“Massachusetts is a better place because of his thoughtful, principled leadership on issues like voter registration and public records reform. And he was an unwavering voice for the most vulnerable in our communities. To Peter, everyone was important and no one was invisible.”