Lieutenant Sean Williamson was killed in the fire. He was a 27-year veteran of the department most recently assigned to Ladder 18.
PHILADELPHIA (WPVI) -- Federal and local investigators are probing a building collapse that killed one firefighter and injured several other people following a fire Saturday morning in Philadelphia's Fairhill neighborhood.
Remembering a Fallen Hero
The blaze broke out around 2 a.m. at a three-story restaurant and residential building on West Indiana Avenue. The fire had been put out, but then the building collapsed at 3:24 a.m.
Lieutenant Sean Williamson, 51, was killed.
Four other firefighters and an inspector with the city's Department of Licenses and Inspections were also trapped at the time of the collapse. One firefighter jumped from the second story of the rubble.
Williamson was a 27-year veteran of the Philadelphia Fire Department and was most recently assigned to Ladder 18 in the city's Hunting Park neighborhood.
"It's going to be a rough few weeks coming up," 1st Deputy Fire Commissioner Craig Murphy said Saturday.
Three firefighters and the L&I worker have been released from Temple University Hospital. One firefighter remains hospitalized in critical but stable condition.
The names of the injured members during the emergency response were:
"You can't predict this," Murphy told reporters at a news conference. "This was just a catastrophic accident that (has) really hurt our department."
Fire Commissioner Adam Thiel told reporters Saturday evening that rescuers "were able to communicate with" Williamson and another firefighter for most of the several hours they remained trapped; but he said, because of the degree of the collapse and where Williamson was located within the structure, they "were not able to save him."
Thiel said the former Marine was "highly respected throughout our department" and had trained "countless" cadets.
Williamson is to have a "full honors" fire department funeral "and given the outpouring of support that I've seen and we've seen as a department, you can expect this to be a pretty large event," Thiel said.
"We're absolutely grieving, we're mourning," Thiel said. "We have a lot more crying and a lot more processing to do this unfolds as we move forward with properly honoring Lt. Williamson," he said.
Mayor Jim Kenney called it "a heartbreaking day for our city."
"For more than 27 years, he dedicated his life to serving and protecting the people of Philadelphia, and sacrificed his life protecting others," Kenney's statement said. "Early (Saturday) morning, like every day, he exemplified heroism by doing what our first responders do every day: put on their uniform, leave their loved ones, and carry out their sworn duty to protect and serve the residents of this city."
The Investigation
On Sunday, ATF National Response Team joined local authorities to begin a joint investigation into the fire.
"Anytime a firefighter loses his/her life in the line of duty, it is a tragic loss to the community," said Matthew Varisco, Special Agent in charge of ATF's Philadelphia Field Division. "We are heartbroken for the families of these firemen and vow to work alongside our partners with the Philadelphia Fire Department and the Philadelphia Fire Marshal's Office to determine the origin and cause of this fire which resulted in the death of one firefighter and injuring of another."
Murphy said the building had been affected by the fire, but it was unclear what caused it to come down.
According to L&I, the property had a lengthy record of investigations and multiple failed violations. Some violations were issued to the previous restaurant which has since gone out of business.
A neighbor's security camera didn't capture the collapse, but video did capture moments after when a plume of smoke and debris took over the surrounding area.
Officials say the collapse happened very quickly with no warning.
The Associated Press contributed to this report.