NORTHAMPTON — Superior Court Associate Justice Francis E. “Frank” Flannery, appointed to the bench in 2018 after a more than 20-year career that included serving as assistant district attorney in the Northwestern District Attorney’s Office, died over the weekend, according to information released by his former Southampton law office. He was 57, and a cause of death was not available Monday.

In a Facebook post, the Law Office of Parker & O’Grady announced the death of Flannery, of Holyoke, describing him as a cherished former member of the firm whose legacy will not be forgotten.

“His dedication to justice, commitment to excellence and deep compassion left a lasting impact on colleagues, clients and the wider legal community,” the law firm wrote. “Frank was not only a respected legal mind but also a mentor and friend to many. His sudden loss is deeply felt by all who had the privilege of knowing him.”

Before being nominated by then-Gov. Charlie Baker and appointed to the Hampden County Superior Court bench, Flannery served as first assistant district attorney at the Hampden County District Attorney’s Office, prosecuting cases before the Superior Court and supervising the offices’ trial and appellate attorneys. From 1998 to 2008, he was assistant district attorney for the Northwestern District Attorney’s Office and chief of its Elders and Persons with Disabilities Unit.

Northwestern First Assistant District Attorney Steven Gagne said whether representing clients, working as a prosecutor or serving as a judge, Flannery had an even-keeled demeanor and was a consummate gentlemen.

“His loss leaves a giant void in the western Massachusetts legal community,” Gagne said.

Gagne said Flannery’s death has also hit really hard in the office, where many knew Flannery personally from his decade-long tenure.

David Rist worked as the criminal trial manager at the Northwestern District Attorney’s Office.

“Frank cared deeply about his work, to do the right thing as a prosecutor,” Rist said. “He was always professional and a good friend to many.”

Hampden County Superior Court Chief Justice Michael D. Ricciuti also issued a statement about Flannery’s death, saying it is a loss to colleagues in the region, the court system and the commonwealth.

“Judge Flannery’s dedication to justice, commitment to excellence and deep compassion has left a lasting impact on the legal community in western Massachusetts,” Ricciuti said.

Hampden County Sheriff Nick Cocchi also offered condolences, calling Flannery “firm, but fair.”

“He was highly regarded by everyone who knew him and will be missed,” Cocchi said. “Our thoughts are with his family and friends in this difficult time.”

Flannery earned his doctorate in law from Willamette University in Salem, Oregon, in 1994, five years after earning his bachelor’s degree from the University of Massachusetts.

In nominating Flannery to the Superior Court, Baker cited his experience in two district attorney’s offices in the Pioneer Valley.

“He has the knowledge and temperament to preside over the wide variety of important civil and criminal cases that come before the Superior Court,” Baker said.

At his 2018 hearing before the Governor’s Council, which reviews and recommends judicial appointments, co-assistant District Attorney Jennifer Fitzgerald described Flannery as someone who listens to everybody, is fair to everybody and offers “sound advice in a comforting, witty and humorous way.” She praised his handling of the most serious cases, including numerous drug cases with tests falsified by a state chemist.

“I consider Frank to be one of the finest colleagues I’ve had the opportunity to work with,” Fitzgerald said.

Scott Merzbach can be reached at smerzbach@gazettenet.com.