Newly obtained video shows the hellish conditions of a Brooklyn house fire that claimed the life of a 31-year-old firefighter and an autistic man who lived at the residence.

The footage, shot by a neighbor before the FDNY arrived, captures bright orange flames and heavy black smoke pouring out of the two-story Canarsie home on Avenue N on Sunday afternoon.

“Just devastating. I have never seen anything like this,” a woman witnessing the horror can be heard saying on video.

FDNY smoke-eater Timothy Klein, 31, and resident Carlos Richards, 21, perished in the fire that caused the home’s second floor to collapse, authorities said.

Eight of Klein’s FDNY comrades also were injured — either in the collapse or from burns, officials said. Some of the firefighters were forced to leap from the windows as the flames turned deadly.

Klein, a six-year veteran of the department, became separated from his fellow firefighters and died when the second-floor caved in, officials said. His funeral will be held Friday in Queens.

Richards, who was autistic, was alone at the time and could not escape his room, according to family members.

“He didn’t know what to do,” Richards’ grandmother Phyllis Foye, 71, said. “He was frightened by all the smoke.

The cause of the fire was still under investigation.

“When a collapse happens, it takes forever to find out [a fire’s cause] because everything’s destroyed,” an FDNY source told The Post. “It’s not like you can see a black spot around an outlet.

“They also probably ripped the s–t out of the place just trying to get [Klein] out,” the source said. “Especially with collapses, you can’t really tell” where victims might be.