James Armand had just bought his son’s school supplies and uniforms.

His brother, the first in the family to attend college, had acquired all the requisites of a new academic year: a laptop, books, clothes.

But in the few minutes it took Thursday for a ravenous fire to sweep from basement to roof of the Dorchester triple-decker where the family lived, it was gone. All of it, gone.

“I don’t know what we’re going to do,” said Armand, staring at the smoldering structure hours later.

The toll was evident in his dejected face, and in the arithmetic of loss: Nine people who lived at 5 Fairmount St., were left without a home. Two were treated for anxiety. Four firefighters had injuries that are not believed to be life-threatening. The financial loss hovered at $300,000.

The fire started in the basement and chewed through the walls, which seemed to have lacked modern fire safety features, said Fire Department spokesman Steve MacDonald.

Once in the walls, the flames raced toward the roof, spreading across each floor along the way. Firefighters were ordered to evacuate the building, and the focus shifted to containment when flames filled the home, MacDonald said.

“You could see the smoke rising in the house through the windows,” said Aaron Hodges, 27, who watched the fire from his home across the street. “It filled up each floor as it went, then the flames would follow, and soon they were shooting out the roof.”

BILL BRETT FOR THE BOSTON GLOBE

Firefighters were ordered to evacuate the building, and the focus shifted to containment when flames filled the home. “By the time I ran back to the front of the house to go in and grab some things, I just couldn’t do it,’’ James Armand said

The first hint of trouble emerged as smoke seeped through floor vents. Maybe it was just a small ember in the basement, Armand thought. He figured he would get his family out, then douse the flames.

Within minutes, smoke consumed the house and blanketed adjacent streets.

All Armand could do was watch.

“I didn’t think it was going to be this big,’ said Armand, who lives on the first floor with his mother and brother. “I thought I’d try to put it out myself. But the smoke was too much. It was coming too fast. There was nothing I could do.”

Firefighters were summoned at 11:12 a.m. They found heavy smoke coming from the basement and the fire extending upward.

“By the time I ran back to the front of the house to go in and grab some things, I just couldn’t do it,’’ Armand said. “I couldn’t even get in.”

About 140 firefighters and numerous engines and ladder-trucks were on the Dorchester street to battle the five-alarm fire, MacDonald said. Crowds gathered for hours while smoke drifted through neighborhood streets several blocks from the blaze.

Shortly after 1 p.m., firefighters were still jetting seven streams on the fire, including three from aerial ladders. By 3 p.m., the fire had exhausted itself, MacDonald said.

“They surrounded it from all four sides and put water on it,” MacDonald said. “The firefighters did a tremendous job keeping it from going into the buildings on either side.”

Armand’s family will be moving in with their cousins who live nearby, said Hansey Lafond, 25, Armand’s cousin, who stood with him Thursday. Lafond said the family’s greatest concern was for Armand’s younger brother, Tony, who is attending Lynn University in Florida.

“Our cousin who has a full scholarship to a university lost all his books, his computer, all his stuff,” Lafond said. “We’re going to make sure he has what he needs, but I hate that he has to go back with all this going on at home.”

They are a family sustained by faith, a faith that knows well the familiar passage from the 23d Psalm, a favorite of Armand’s grandmother: “Even though I walk through the valley of the shadow of death, I will fear no evil, for you are with me.”

“Everything happens for a reason,” Lafond said. “We’ll bounce back from this.”