The burning building had been vacant for years, but the firefighters went in anyway just in case squatters started the blaze and were trapped inside. Then the heavy-timbered roof and a wall suddenly collapsed.
Four firefighters were trapped under debris, and two of them died on a day that already was among the most somber on the Chicago Fire Department's calendar. Exactly 100 years ago, 21 Chicago firefighters died when a wall collapsed at the Union Stock Yards fire, one of the nation's worst tragedies for firefighters before 9/11.
"We were ringing the bell and calling out the names," said retired fireman Bill Cosgrove, who was at a service honoring the anniversary. "We heard a mayday on the radio that a wall had fallen in."
Most of the firefighters at the service broke down in tears when they found out about the collapse, he said.
"It was beyond disbelief," Cosgrove said. "It was a matter of a few hours and a hundred years later we have the same type of incident."
He said that two firefighters at the memorial left to help dig out their colleagues. Other off-duty firefighters rushed there as well, said Fire Department spokesman Larry Langford.
They joined more than 170 other firefighters on duty who responded to a 911 call about the burning building just before dawn on Wednesday, Langford said.
He said that no one expected the call to be anything more than a routine winter fire.
Although the decades-old, one-story building had been vacant for years and the utilities had been turned off, firefighters searched it out of concern that homeless people might be inside trying to stay warm.
The cause of the fire was under investigation. Authorities speculated that squatters might have been burning debris to keep warm.
"The fire had no other way of starting," Langford said. He said that the only people injured were firefighters. The men killed were Edward Stringer, 47, a 12-year department veteran, and Corey Ankum, 34, who joined the department a little over a year ago. They and two others were trapped under the roof debris.
Two firefighters were pulled out quickly but rescuers had to use extrication equipment to reach the other two.
Every firefighter at the scene on Wednesday "did the best they could to save their brothers," said Robert Hoff, the city's fire commissioner.
In all, 17 firefighters were injured, and five remained hospitalized Wednesday evening, Hoff said.
Hoff and firefighter's union chief Tom Ryan spoke at an emotional news conference hours after the blaze.
"No matter how much experience you have on the job," Ryan said, "a morning like this still takes you by surprise." Ryan said the victims' families "can take solace in knowing that their husbands, their fathers, their brothers are heroes."
Mayor Richard Daley was out of town at the time of the blaze but cut his trip short to return home and address the city.
At a news conference Wednesday evening, a tearful Daley said he'd known Ankum and his family well. Ankum's wife, Demeka, has worked as Daley's executive assistant for about 10 years.
He remembered Ankum as a wonderful husband, father and firefighter who loved his job. "That's all he wanted to talk about," Daley said.
"Each and every time we lose a member of the police and fire departments, we lose a part of Chicago's history," Daley said. Ankum's brother, Gerald Glover, said he had been with the department for about a year and had a wife and three children. "He was a great young man. He would do anything for anybody. He would give you the shirt off his back," Glover said. The day's somber events were felt department-wide, fire officials said. Posted at the department's training academy was an electronic sign flashing photographs of Ankum and Stringer, along with a message reading, "We wish a speedy recovery to all CFD members injured this day."
It was unclear why the building's roof and wall collapsed. Hoff said snow, ice, and the building's age could have contributed.