LOWELL — A six-alarm fire ravaged a multifamily home in Centralville on Thursday, displacing 22 residents, and hospitalizing four firefighters and one resident, all with non-life-threatening conditions.

The cause of the blaze at 73 Aiken Ave., first reported to firefighters at about 11:30 a.m., is under investigation.

The blaze was under control about an hour and a half after the initial call. As firefighters conducted an overhaul of the charred three-story building, Lowell Fire Chief Phil Charron told members of the press at the scene that he could not definitively say if the structure was a total loss, but added, “If I were a betting man …” suggesting the building had been destroyed.

Further devastation may have been prevented by Frank King and his 25-year-old son, Austin King. The pair, who work at DeRosa Properties on Farmland Road, saw the smoke a few blocks away and went to check it out. Frank King said they pulled up to find “black heavy smoke” pouring from a first-floor unit located on the front right side of the building when facing the structure.

“We heard a window break from the heat, I’m assuming, and the flames just really kicked up a notch,” Frank King said. “It was ripping.”

At that point, firefighters had not yet arrived on scene. Frank King said there were people outside the building videotaping the burgeoning flames. He asked them if anyone was inside, but they were unsure. Concerned, Frank King said he and his son entered the structure to ensure everyone was out.

Frank King said he went to units on the first and second floors, finding people who were unaware of the fire building inside the structure. Austin King, meanwhile, helped an older woman out of an apartment in the back.

“I didn’t go too far because the smoke and the heat in that hallway were insane,” Frank King said. “As soon as I kicked open that doorway, you could feel a change in the temperature.”

He captured video showing bright orange flames overtaking the building and black smoke billowing from it as firefighters arrived on scene.

Property records indicate that the wood frame building, constructed in 1890, contains 25 rooms. Charron said the building comprises six separate units.

The fire chief explained that the blaze escalated to six alarms to bring in the necessary manpower to subdue the flames. He estimated about 55 to 60 firefighters were active at the scene.

At one point, firefighters conducting an interior attack on the flames were called to exit the building due to the extreme conditions.

“There was a very intense fire condition in the attic,” Charron said. “The fire companies had to evacuate when the fire flashed over. They had to bail out pretty quickly.”

According to Charron, one firefighter had to jump out a window, while others took the stairs.

In total, 11 firefighters were evaluated by emergency medical services at the scene, with four hospitalized. Additionally, a resident of the building was hospitalized due to smoke inhalation.

From the scene, Jordyn Hoar, a resident of Bridge Street, said she knows the woman who was hospitalized. Hoar said the woman lives in the first-floor unit located on the front right side of the building with her husband and four children, who were at school at the time of the fire.

Hoar said she was told that the woman and her husband heard an alarm going off in the apartment and when they opened the bedroom door, they were met with a wall of flames.

According to Hoar, two puppies that lived in the apartment were killed in the fire.

Hoar said when she heard about the blaze, she rushed over to check on the family and was shocked by the extent of the damage.

“It was a crazy scene,” Hoar said. “Something I don’t think I’ll ever really get out of my mind.”

Charron praised the firefighters for doing an “excellent job” and thanked the mutual aid companies. He said firefighters came to help from as far away as Nashua, N.H. and Burlington.

The Red Cross was called to help those displaced. The Salvation Army’s Emergency Disaster Services Canteen from Lowell was also on hand, providing food, hydration, and emotional support.

“The Salvation Army’s EDS is working with emergency management partners to identify ongoing needs for survivors and is available for emotional & spiritual care to first responders and displaced residents,” they said in a statement released on Thursday. “The Salvation Army’s Lowell Corps and Community Center is also prepared to assist the displaced with future needs, including social services, and will work alongside partner organizations.”

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