Mr. Mahoney's wife, Pat, said he was not feeling well when he came home from work, so she took him to Bryn Mawr Hospital, where he died. He had not been sick and did not have any known heart problems.
"He was my best friend," she said through tears Friday.
For more than two decades, Mr. Mahoney was a likable behind-the-scenes player in the city's business and political affairs, the guy who knew whom to call to make things happen.
City Councilman James F. Kenney knew Mr. Mahoney from his visits to City Hall over the last 20 years as the chamber's most familiar face. Kenney called him "thoughtful, informed, calm."
Mr. Mahoney's good reputation among Council members, and affable personality, got him access with everyone, including more liberal members not always friendly to the chamber's business-centric issues.
"He broke through on a personal level," Kenney said. "Joe was able to get a sit-down, get an ear, and get a listen-to."
He was most comfortable out of the spotlight, recalled Pizzi.
"It was never about him. It was always about the issue, and he never got in the way of elected officials," he said. "Everything I got credit for in 13 years at the chamber, it was because of the work he did."
Mr. Mahoney learned his leadership skills growing up as the eldest of three boys, said his brother the Rev. Shaun Mahoney. He was born in West Philadelphia, then moved with his family when he was in first grade to Bala Cynwyd. He attended Archbishop Carroll High School and St. Joe's, where he studied political science.
He remained passionate about politics and his alma mater his entire life, said friends and family. Before working at the chamber, Mr. Mahoney served on the staff of Republican U.S. Rep. R. Lawrence Coughlin.
St. Joe's is also where he met his future wife. They were just friends, but years later they met at a function and hit it off. They married 19 years ago. It was a first marriage for both.
Together, they opened Brooks Gift Gallery in Drexel Hill, selling luxury items for weddings and other occasions. Pat worked in the store while her husband did the bookkeeping and tended the website.
In a statement, Mayor Nutter said: "Joe cared passionately about our city and region. Whatever the issue, Joe would often be the first to lend a hand or give an opinion."
Chamber president and CEO Rob Wonderling said in a statement, "The passing of Joe Mahoney is a tremendous loss to the city and region. Joe made a difference in the lives of so many people throughout our community. He loved Philadelphia and will be greatly missed by all who had the honor to know him."
At the chamber, he oversaw public-policy activities at the federal, state, and city levels as well as outreach to governments in the surrounding counties. From working with Sister Mary Scullion on homeless issues to trying to making sure Philadelphia's tax policy was competitive, "he understood the right approach with elected officials, and even when they were on a different side, he always held everyone in respect," Pizzi said, adding, "He dedicated his entire life to the region."
The Mahoneys were very active in St. Joe's alumni association, while Mr. Mahoney was chairman of the Erivan K. Haub School of Business board of visitors.
"He was the best. He was a good friend," said Joe DiAngelo, dean of Haub. "He's been a permanent fixture around here."
He and his wife, he said, "are true Hawks" who raised hundreds of thousands of dollars for the university.
Just last week, he said, Mahoney was master of ceremonies for the school's annual hall of fame dinner. "He was very good at doing that," he said.
He also took charge three years ago when his father died, said his brother. As the eldest son, he sold his parents' house and helped his mother relocate.
"He really stepped up to the plate," he said.
Besides his wife and brother, Mr. Mahoney is survived by his mother, Edna; another brother, Dennis; and nieces and nephews.
Funeral arrangements were incomplete.
Contact Kathy Boccella at firstname.lastname@example.org, 610-313-8232 or follow @kathyboccella on Twitter.