Firefighter Jimmy Lee speaks to reporters at the Rescue Comapny 1 firehouse on West 43rd Street. View Full Caption DNAinfo/Maya Rajamani

HELL’S KITCHEN — A firefighter who dangled from a rope over a deadly Upper East Side inferno to rescue an 81-year-old man from his fifth-floor apartment shortly before it was engulfed in flames Thursday said later that there had been “no time to think,” just act, in the moments before the rescue.

Firefighter Jimmy Lee’s colleagues tied a rope to an object on the roof, attached it to a harness and lowered him down to the man’s fifth-floor window with only moments to spare, Lee told reporters outside the FDNY's Rescue Company 1 firehouse on West 43rd Street Thursday morning.

“Once I went over [the side of the building], I couldn’t see anything,” he recalled. “The smoke was very thick.”

As he approached the window, Lee saw the man inside his apartment, crouched over with his hood up to protect his head, he recounted.

“I sort of reached in and said, ‘Let’s go,’” he said. “I didn’t really think too much.”

Photo courtesy FDNY

After Lee grabbed the man and held on tight, firefighters on the roof lowered the two of them down to the ground, he said.

Not long after they landed safely, Lee looked back up and discovered the rope they’d been lowered down on had burned through. The man’s apartment windows, meanwhile, were “fully engulfed in fire,” he added.

“We were both very happy to be on the ground when we saw that,” he said. “It was getting very bad.”

WATCH: Video of this morning's daring roof-rope rescue by #FDNY members at a 6-alarm fire on the #UES. Video credit Pete Billis A video posted by FDNY (@fdny) on Oct 27, 2016 at 2:25pm PDT

The massive blaze ripped through three buildings near First Avenue, leaving one man dead and 16 other people injured after breaking out around 3:30 a.m. Thursday.

The 81-year-old was listed in critical condition as of Thursday morning after suffering burns and smoke inhalation, officials said.

In his 13 years with the FDNY, Lee had never performed that kind of rescue before, as it's a “fairly risky” move.

Firefighters use the rescue rope method as a "last resort," FDNY Assistant Chief Roger Sakowich noted at the scene of the fire earlier on Tuesday.

“We don’t want to use a rope if we don’t have to, but [the victim] didn’t have much time,” Sakowich said. “If they didn’t get to him when they got him, he wasn’t going to have much longer.”

Every firefighter in the city trains to carry it out, Lee noted.

“There’s no time to think when [the rescue is] on,” he said. “We drilled hard on it, and it’s something that’s ingrained in your head from the day you come on the job in the fire academy to the day you retire.”

Lee's next stop was his daughter’s school, where he’d promised to celebrate her fifth birthday Thursday with cupcakes, he said.

The rescue was a “total team effort,” he said.

“Without all the guys, the operation wouldn’t have happened,” he said. “I just happened to be the guy on the rope.”