State Rep. Mike O'Brien, a lifelong Philadelphian and strong advocate for the city's public schools, died early Monday of a heart attack in the Fishtown home where he grew up. He was 64.

Mr. O'Brien, a six-term House Democrat who was the party's chair of the Urban Affairs Committee, had announced in July that he would not seek reelection for a seventh term, citing health reasons. His chief of staff, Mary Isaacson, had replaced Mr. O'Brien as the party nominee for the 175th District seat  representing the city's river wards.

"You always knew where you stood with him, good or bad," said Isaacson.

Isaacson said members of Mr. O'Brien's family told her that he woke early Monday and was having difficulty breathing and then suffered a heart attack, dying before an ambulance could arrive. Mr. O'Brien had been dealing with health issues for several years, including diabetes and a lingering infection in one of his feet.

In Mr. O'Brien's memory,  Gov. Wolf ordered flags to fly at half-staff.

"Mike cared deeply for his community and demonstrated his commitment each day he went to work," Wolf said in a statement.

Mr. O'Brien attended Northeast Catholic High School for boys and graduated from La Salle University. Before entering politics, he was a butcher and a director of operations at a meat business in Philadelphia.

Eventually he became involved in politics. He served as the chief of staff for his predecessor in the 175th District, Marie A. Lederer, for 12 years before being elected to the state legislature in 2006. Isaacson succeed him as chief of staff.

"He was the best mentor I could ever have," she said.

Mr. O'Brien, whose wife, Rita, is a schoolteacher, introduced legislation to save schools from layoffs and program cuts by redirecting state funds to cover the school district's deficit.

In 2014, he proposed that the city elect school board officials; unlike in other districts, board members in Philadelphia are appointed.

"The blame game has to end. It ends with an elected board that assumes ultimate responsibility and can provide a clear, unbiased funding plan for our schools and our children," he said at the time.

"He was a proud progressive Democrat who was not afraid to fight against the Republican majority," said U.S. Rep. Kevin J. Boyle (D., Pa.).

In 2012 Mr. O'Brien opposed the state's voter-ID laws, and in 2013 he introduced a bill aimed at helping property owners affected by significant property-tax increases under the city's new assessment system.

He supported equal pay for women and introduced legislation to protect whistle-blowers who spoke  out against harassment and discrimination.

RIP to my friend and colleague State Rep. Mike O’Brien who died this morning. He was such a passionate and genuine man…

Posted by Kevin Boyle on Monday, October 15, 2018

Praise for Mr. O'Brien was bipartisan.

"Rep. O'Brien was a strong voice for the citizens of Philadelphia during his 12 years in the House and a man of common sense and integrity," Speaker Mike Turzai (R., Allegheny) said in a statement. "Despite facing health issues, Rep. O'Brien never stopped working hard for his constituents and the people of Pennsylvania." 

Local politicians took to social media to offer condolences and reminisce about what O'Brien meant to Philadelphia.

"Mike embodied everything public service is about – helping people who need help, never expecting anything in return along the way," City Council President Darrell Clarke said in a statement. "Rest easy Mike."

In addition to his wife, O'Brien is survived a daughter, Bridget, a doctoral candidate at Notre Dame, and son, Michael, a research scientist at the Chesapeake Biological Laboratory.

Funeral arrangements were pending.