Loved ones, hundreds of fellow firefighters and city dignitaries including Mayor Eric Adams gathered Thursday to pay their respects to fallen FDNY firefighter Timothy Klein, who mourners said was “beloved at the firehouse.”

Klein, a 6-year FDNY veteran and the son of a retired firefighter, was killed in a raging Sunday afternoon house fire on Avenue N near East 108th Street in Canarsie.

“The Klein family set a standard for what a family should be,” Bo Healey, 75, a friend of the Kleins who was at the wake, told The Post. “You’ll never find a better family.”

Acting Commissioner Laura Kavanagh said it “was an incredibly heartbreaking day for us, for the department, for the family.”

“Tim Klein is the 1,157th member to die in the line of duty…it doesn’t make it any easier,” she added, describing him as “the best firefighter, the best son, the best brother, the kind of the guy that everyone relied on.”

On one side of Klein’s casket was a New York Rangers jersey with the number 8 and his last name, and on the other side sat his helmet. 

Klein, 31, was dressed in FDNY garb in the casket, and in the viewing room, photos of him lined the walls. In one, he and his girlfriend are dressed for a night out. In another, they’re both in Rangers uniforms smiling for the camera. 

Other photos showed Klein with his fellow firefighters and Klein as a kid with his brothers. Almost all the pictures showed him with a big grin. 

That big smile never went away, Klein’s Lieutenant Robert Kittelberger, said.

“He was the sweetest kid I’ve ever met… he had a smile on his face 24 hours a day,” Kittelberger said Thursday.

Klein’s viewing began at 2 p.m at McManus Funeral Home, 4601 Avenue N in Flatlands, Brooklyn.

The funeral for the hero who grew up in Breezy Point will be held at 11 a.m. Friday at the Church of St. Francis de Sales, 129-16 Rockaway Beach Boulevard in Belle Harbor, Queens. 

Fire officials say smoke-eaters were battling the fire when flames suddenly swept through the second floor of the building, sending them leaping from windows as part of the structure began caving in on itself.

Klein was fatally injured in the structural collapse, according to authorities and sources.

On Thursday firefighters wearing their dress blues saluted as Klein’s family made their way inside McManus Funeral Home.

Acting Chief of Dept. John Hodgens said Klein was “beloved at the firehouse” and volunteered with Fight for Firefighters, which builds ramps to help those in wheelchairs.

“They built 30 of these since the organization began for people in need and Tim did not miss one of those 30 builds,” Hodgens said.

Three years ago, Klein gave a eulogy for fellow Bravest Steven Pollard, who died on duty while helping at the scene of a Brooklyn car crash.

A 21-year-old autistic man, identified as Carlos Richards – the son of a retired NYPD cop – also died in Sunday’s inferno. 

Richards was reported missing by his family when flames broke out in their home, authorities said.

Later Sunday, Richards’ body was found in the home’s charred remains, authorities said. 

“Our condolences go to the family of the firefighter who died trying to save Carlos,” a man told The Post by phone Monday, after answering a number listed for Richards’ mother. 

“Our hearts go out to his family. Right now, we’re grieving for Carlos, and we share the same pain that they are feeling,’’ added the man, who did not identify himself.