Mark Keeley was only 19, fresh out of Cardinal Dougherty High School when he joined his father last year as a full-time PGW employee.
At the accident site, PGW and local, state, and federal investigators have begun to search for answers to what caused the explosion.
It's a problem experts said they have seen many times before.
"This type of explosion isn't that unique. It happens every four or five days," said Carl Weimer, head of the Pipeline Safety Trust, an advocacy group in Washington state.
Finding answers could take months - or longer. Federal investigators are still searching for the cause of a September gas explosion in California that killed eight people and destroyed dozens of homes.
At Torresdale Avenue and Disston Street on Wednesday afternoon, about 200 people gathered to gaze at the wreckage.
Geraldine Dixon, 48 - a care worker at the Disston Manor Personal Care Home, about a block from the Disston Chiropractic & Rehab Center, where the explosion occurred - said firefighters came to the nursing home Tuesday night and told residents the building was being evacuated. Dixon said she and others quickly walked about 22 residents to the Disston Recreation Center two blocks away.
"No sooner than I got them inside the building, the first explosion went off," Dixon said. "I came running out, and there were flames everywhere."
She said papers from the chiropractor's office were raining down up to three blocks away.
"It was like it was snowing," Dixon said, adding that the entire second floor of the chiropractic office was blown onto the roadway on Disston.
By midday Wednesday, residents in all but three homes had been allowed back to their houses. About 40 people had been forced out.
