BURLINGTON, Conn. (WTNH) — The Burlington firefighter injured in a building blaze in New Hartford earlier this week has died, officials confirmed to News 8 Thursday.

The Burlington Fire Department has officially classified his death as a line of duty death.

Colin McFadden, a 26-year-old firefighter/EMT from Burlington, became suddenly ill and experienced a medical emergency while fighting a large fire at the historic New Hartford House overnight Tuesday.

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He was brought to John Dempsey Hospital where he was initially listed in critical condition. During his care and treatment, McFadden’s medical team discovered a previously undiagnosed medical condition that caused the sudden illness.

Burlington’s fire chief announced Thursday afternoon the medical condition McFadden was diagnosed with was Acute Promyelocytic Leukemia (APL), a rare, adult, acute myeloid leukemia.

Each year in the United States it develops in 2.2 people per million for a total of 600-800 people. The signs and symptoms of APL include an increased risk to both bleed and form blood clots. People may also experience excessive tiredness, pain in affected areas, loss of appetite, and weight loss.

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Officials said McFadden was a six-year veteran of the Burlington Volunteer Fire Department.

Burlington Fire Chief Michael Boucher described the 26-year-old as “an amazing kid. He came in here a young guy at 20 years old. He pours his heart and soul into everything he does, he’s even a little bit quirky and we all kind of bust on him for that but that was us showing him some love. He became a firefighter and an EMT, and he’s one of those guys who was always at the station, and always jumping on the truck when there was a call.”

Black bunting hangs outside the Burlington Fire Department

Matt Boyne got to know firefighter McFadden when McFadden volunteered at the Hartford Area Habitat for Humanity ReStore in Bloomfield.

Boyne remembers a young man with a sharp sense of humor — quick witted with his one liners. He says McFadden enjoyed helping others, was extremely organized, focused, and encouraged other volunteers.

“He was a giver. Doesn’t matter how you do it, he gave a lot of things to a lot of people. All of the people he was around, the people he worked with, his classmates, they’ll say the same things. I don’t know how you can say anything bad about him. He was a sweet soul,” Boyne said.

At a press conference Thursday, Chief Boucher read a statement from McFadden’s family, who expressed their gratitude for the staff at John Dempsey Hospital.

Chief Boucher also addressed the blood shortage the state is facing, a problem he said that may have impacted McFadden’s treatment. A blood drive will be held at Burlington Town Hall on Saturday from 8 a.m. to 3 p.m. McFadden’s family is encouraging everyone who can to come out and donate.

The Burlington Fire Department is also asking for any donations to be made to organizations close to Colin’s heart, including the Gengras Center in West Hartford. Funeral arrangements for Colin are still being made.

The investigation into the cause of the fire is ongoing.

Calling hours for Firefighter McFadden’s service will take place Wednesday, Aug. 18, from 3-8 p.m. at the Funk Funeral Home at 35 Bellevue Ave. in Bristol. A mass will be held Thursday, Aug. 19, at 11 a.m. at Saint Matthew Church at 120 Church Ave. in Bristol. A burial will follow at Saint Joseph Cemetery at 522 Terryville Ave., Bristol.

Following McFadden’s death, Governor Ned Lamont ordered the US and state flags in Connecticut to be lowered at half-staff in McFadden’s honor.

It is with a heavy heart that we mourn the passing of Burlington Firefighter Colin McFadden, who responded early Tuesday morning to a tragic fire out of a courageous sense of duty and compassion to protect the lives of others. This is a terrible reminder of the dangers that firefighters put themselves in each time they respond to an emergency. My deepest sympathies go out to his family, friends, and fellow firefighters from the Burlington Volunteer Fire Department.”

Governor Ned Lamont

Fire departments from across the state also offered condolences for the loss of firefighter McFadden:

McFadden is the second Connecticut firefighter to die following injuries sustained while on duty this year. New Haven Firefighter Ricardo Torres Jr. died back in May while battling a fire on Valley Street in New Haven.