The deaths of Debbie Reynolds and Carrie Fisher in the span of 48 hours have left the team behind the upcoming HBO documentary on the mother and daughter reeling from shock.

“Bright Lights: Starring Carrie Fisher and Debbie Reynolds” is a chronicle of the extraordinary bond that mother and daughter forged over six decades in the unrelenting glare of showbiz’s spotlight. Documentary vets Fisher Stevens and Alexis Bloom directed the film, which screened in October at the New York Film Festival and before that in May at Cannes.

“It’s a love story,” said HBO Documentary Films president Sheila Nevins told Variety Wednesday night after the news broke of Reynolds’ death at the age of 84. On Friday, HBO set a premiere date: Saturday, Jan. 7 at 8 p.m.

“Carrie wanted to make ‘Bright Lights’ for Debbie and Debbie wanted to make it for Carrie,” Nevins said. The sudden loss of the two women only magnify the importance of Fisher and Bloom capturing the material for the movie when they did.

Fisher died unexpectedly Tuesday at the age of 60 following complications from a heart attack suffered during a flight from London to Los Angeles. The twin blows have been overwhelming to all of those involved in “Bright Lights,” Nevins said. “If this was a Hollywood script, no one would believe it,” she said, fighting back tears. “They just loved each other so much. The bond was just unbreakable.”

Much of the footage for “Bright Lights” was shot about a year ago. The movie depicts the intensely close relationship that mother and daughter maintained through all their personal and professional ups and downs. Fisher in the movie is candid about her recent battles with mental illness.

“It’s life with Carrie and Debbie. It’s about both of them trying to stand upright, both having their frailties — age on the one hand and mental illness on the other. It’s a love story about a mother and daughter — they happen to be Carrie and Debbie,” Nevins said.

Directors Stevens and Bloom paid tribute to the pair in a joint statement. The two spearheaded the project for HBO Documentary Films.

Fisher and Reynolds “were supremely kind human beings, and unusually perceptive. And when either one entered a room, the energy changed. Quite simply, we were iron filings to their magnets,” the directors said. “And never more so than when they were together. These women were more than mother and daughter, they were an expression of exquisite humanity in all its travail and triumph. They lived their days boldly. They sung every song worth singing (often together.) Carrie and Debbie loved each other profoundly. We are devastated they’re gone. And so very fortunate to have known them at all.”

Carrie Fisher’s goal with “Bright Lights” was to document for a younger generation Reynolds’ legacy as an entertainer — from her wholesome image as the star of the “Tammy” films to musicals such as “Singin’ in the Rain” to her cabaret and comedic chops. “She wanted to preserve all of that for her mother,” Nevins said.

Nevins became friendly with Fisher a few years ago when they worked together on the HBO adaptation of Fisher’s one-woman Broadway show “Wishful Drinking.” The HBO docu chief spoke to Fisher by phone just last week.

HBO will air an encore presentation of “Wishful Drinking” in Fisher’s honor on Sunday at 9 p.m. The film tells the story of Fisher’s life, combining her raucous one-woman stage performance, interviews with family and friends, and archival footage.

Fisher had planned to fly from London to New York to do some work with HBO on “Bright Lights,” Nevins said, but she changed her mind and headed straight to Los Angeles to spend Christmas with Reynolds and other family members.

Nevins last spent time with Fisher in London in June. She was in good spirits and racing to finish her latest memoir, “The Princess Diarist,” about her experiences on the first three “Star Wars” films. There was already talk of turning that book, published last month, into another one-woman show and HBO special, Nevins said.

“Carrie wanted to be well even when her mind didn’t let her be well,” Nevins said. “She was perfectly brilliant.”