A procession lead by ambulances carrying the bodies of the four fallen firefighters drive to the Forensic Center of Harris County to be examined, Friday, May 31, 2013, in Houston. The firefighters died fighting a five-alarm fire at the Southwest Inn earlier in the day. (Cody Duty/Houston Chronicle photo)

HOUSTON (Houston Chronicle) - What started as a small restaurant fire - a bit of business faced daily by firefighters everywhere - turned into a motel- engulfing inferno that claimed the lives of four responders from the Houston Fire Department when part of the building collapsed on them Friday. It was the department's worst loss of life ever.

FRM/FFN: Houston Firefighters Killed in Five-Alarm Fire

FRM/FFN: Houston Fire Claimed Lives of Varying Rank
Captain, Engineer, Firefighter and Probationary Firefighter perish

"We arrived on the scene and about 14 minutes after our arrival we had a mayday," HFD Chief Terry Garrison said. In an instant or close to it, a group of firefighters who had put themselves in deliberate jeopardy out of concern that people might be trapped inside the Southwest Inn were buried in burning debris.

The precise series of events is at the heart of an investigation to be led by ATF specialists, who arrived at the scene later in the day. But the gist of it was clear in seconds."We had an early and quick catastrophic failure of the roof," Garrison said.

"There's no way that I would have anticipated that we would lose four firefighters. I want to tell the residents of Houston their firefighters acted absolutely courageously today, that there was probably a dozen acts of heroism on that scene."

Across the city people were shocked by news of the loss. In addition to the dead, 13 other firefighters were taken to local hospitals with injuries. One was in critical condition.

"There is nothing that will heal the hurt we all feel," said a shaken Mayor Annise Parker.

Read More on FFN