Celia Sweeney said two bolts came loose from the ladder, causing it to tip over. Sweeney fell about 10 feet and hit his head on the floor.
Mayoral spokesman Mark McDonald said the accident was under investigation.
"It's a terrible tragedy; I still can't believe it," said Celia Sweeney. "He was my best friend. He helped anybody that needed help. He's going to be very missed."
The Sweeneys had been married seven years but were a couple for 25, Celia Sweeney said.
When her husband, a former Marine, wasn't working, he liked to shoot darts, she said, and played in the Quaker City English Dart League.
He also enjoyed spending time with his grandchildren and making family trips to Wildwood in the summer.
"We went to the beach and walked along the boardwalk. We were like little kids when we got down there," she said.
Longtime friend Vincent Fragale, who worked with Sweeney for 15 years before he became the business agent for Local 1927, said Sweeney's main job was to maintain and repair fire ladders.
"He was one of the hardest workers and most straightforward guys I ever met," Fragale said.
Fragale said Sweeney's fellow workers are stunned by his death. "Our hearts are broken. My heart is torn from my chest right now," Fragale said.
This was not the Sweeney family's first experience with a tragic death.
Sweeney's son, Nickie, died in 2008 at age 27, also from head injuries, after he was struck by a Snapple bottle somebody threw during "a night of mischief," Celia Sweeney said.
Besides his wife, Sweeney is survived by daughters Lynnann, 35, and Jessica, 33; a stepdaughter, Vanessa, 31; and 11 grandchildren.
Funeral arrangements were pending.
Contact Michael Hinkelman at firstname.lastname@example.org or 215-854-2656. Follow him on Twitter @MHinkelman.