The nine firefighters who died in South Carolina fighting a blaze that swept through a furniture warehouse died doing what they loved and are heroes to the community they helped save, the Charleston Fire Department chief said Tuesday.

"We lost over 100 years of service to the city of Charleston Fire Department," Fire Chief Rusty Thomas said during a press conference. "To the families — you gave them to us. We protected them as much as we could. They did exactly what they were trained to do."

The firefighters died after the building's roof collapsed upon them. It was the worst death toll for firefighters since the Sept. 11, 2001 terror attacks.

"We will never forget, just like 9/11, we will never forget these nine firefighters who lost their lives last night, doing what they loved to do — fight fire," Thomas said.

The firefighters who died had worked for the department anywhere from 18 months to 30 years. Those killed were: Capt. William "Billy" Hutchinson, 48; Capt. Mike Benke, 49; Capt. Louis Mulkey, 34; Engineer Mark Kelsey, 40; Engineer Bradford "Brad" Baity, 37; Assistant Engineer Michael French, 27; James "Earl" Drayton, 56; Brandon Thompson, 27; and Melven Champaign, 46.

Charleston's mayor said the tragedy was "difficult to fathom or quantify."

"They were heroes," Charleston Mayor Joseph P. Riley told FOX News Tuesday. "They were concerned about people being trapped in the building. They were heroes. They were fighting the fire and the fire overwhelmed them."

The cause of the fire was under investigation, but Riley said arson was not suspected.

Two employees in the building were rescued from the blaze, which broke out at about 7 p.m. Monday in the Sofa Super Store and warehouse, but the disaster has been "difficult to fathom or quantify," he said. The cause of the fire was under investigation, but Riley said arson was not suspected.

"Nine brave, heroic, courageous firefighters of the city of Charleston have perished fighting fire in a most courageous and fearless manner, carrying out their duties," Riley said at a morning news conference. "To all of their loved ones, our heart goes out to them."

President Bush called the loss "devastating."

"These firefighters were true heroes who demonstrated great skill and courage," Bush said in a statement. "Their unwavering commitment to their neighbors and to the City of Charleston is an inspiration to all Americans."

The department has 237 firefighters in 19 companies located throughout the city of about 106,000.

Overnight, firefighters, police officers and other rescue workers saluted as the bodies were carried from the warehouse.

"To lose nine is just a tragedy of immense proportions," Riley said. "To lose nine is just unbelievable."

Police Chief Greg Mullen told The Charleston Post and Courier that Thomas was on scene all night until the bodies of all nine firefighters were removed from the rubble.

"Chief Thomas is a true leader," Mullen told the newspaper.

Thomas met with many families of the victims Monday night.

"I can’t even imagine what the firefighters are going through, it’s just indescribable," Mullen told the Post and Courier. "The way to continue to honor the sacrifice they made is to go back to work and make sure you live up to what they would do if they were still alive. That is their legacy."

Click here to read The Charleston Post and Courier story

Riley said the blaze apparently started in a storage area. He was unsure whether there were sprinklers in the building.

Witnesses said the store's roof collapsed, throwing debris over about two-dozen rescue workers. Onlookers were hit with flying ash.

"It was like a 30-foot tornado of flames," said Mark Hilton, who was struck in his eye.

Eric Glover said in a cable news interview that he and a number of other firefighters were at a golf tournament to benefit the family of a firefighter who had recently died when they heard the call come over their department radios. By the time he arrived, he said, the roof had already collapsed.

"It all happened pretty fast. They didn't really have a chance," Glover said.

"You're always close to the guys because you spend a third of your life with these guys. Every third day you spend 24 hours there, so you get real close," he added.

Daniel Shahid, a salesman at a nearby car dealership, said firefighters came in asking for towels.

"The next thing you know, we were carrying hoses, directing traffic, everybody from the dealership," he said.

Shahid said he saw firefighters rescue four people from the building.

"They were struggling. They were covered in black soot. They looked scared out of their minds," Shahid said.

He later told a cable news network the roof collapsed too quickly for anyone to escape.

"It came from nowhere," he said. "It was a standing structure and five seconds later it was on the ground."

Riley called the firefighters heroes.

"This is a profession that we must never take for granted," the mayor said. "There's a fire raging and they go toward it."

The National Fire Protection Association said the Charleston fire was the worst single incident to claim firefighters' lives since the Sept. 11 attacks, which killed 340 firefighters, two paramedics and a chaplain. It was the deadliest fire in South Carolina since a 1979 blaze killed 11 people in the Lancaster County jail.

On Tuesday morning, flowers were left on the sidewalk in front of the wreckage of the one-story furniture store and its adjacent, slightly taller warehouse, both of which continued to smolder.

"Our thoughts and prayers are with all of you and your families. We are deeply saddened and want you all to know that we value your bravery and thank you for putting your lives on the line to keep us all safe. God bless you all," read one note.

Gov. Mark Sanford ordered state flags lowered to half staff Tuesday.

"These are truly some of South Carolina's bravest, who in this case made the ultimate sacrifice in the line of duty," Sanford said.

The buildings are located on what residents here refer to as the "auto mile," a commercial strip of car dealers, body shops and stereo installers.

The Associated Press contributed to this report.