Patrick Duffy recalled the horrific night his parents were gunned down at their Montana bar 40 years ago — and how he coped with the devastating loss.

The “Dallas” star, 77, said that two teens armed with shotguns returned to his parents’ bar in Boulder, Mont., after his dad, Terrence, kicked them out earlier that evening for getting drunk and causing trouble on Nov. 18, 1986.

“It was very late at night,” Duffy recalled Monday during an appearance on Steve Kmetko’s “Still Here Hollywood” podcast. “There was nobody in the bar except my father and my mother. And they walked in with their shotguns.”

Terrence saw the 19-year-olds — Sean Wentz and Kenneth A. Miller — return and stepped toward them, telling the pair, “I told you to,” before they opened fire, Duffy said, referencing testimony from his parents’ 1987 murder trial.

Duffy’s mom, Marie, who had been working on a crossword puzzle at the other end of the bar, rushed toward her husband but was also shot and killed.

The gunmen then jumped over the bar, grabbed money from the cash register and stole a couple of bottles of liquor before fleeing.

The bodies of Terrence and Marie were discovered by a group of people who stopped for a drink after a shift change at the Montana Developmental Center, a nearby state institution, according to the Los Angeles Times.

One woman initially thought Marie had fainted when she spotted her on the floor, but noticed blood on Terrence and ran outside to alert a friend.

After the killings, Wentz and Miller allegedly stole a pickup truck from a car dealership before visiting Wentz’s 22-year-old girlfriend, who called police after they mentioned people had been shot dead.

Wentz and Miller were sentenced to 190 and 180 years in prison, respectively.

The “Step by Step” star revealed he learned of the tragedy the following morning when his sister, a Washington state police lieutenant, called him in tears on her way to Montana.

After news of the killings made headlines, film crews gathered outside his California home. “Dallas” producers arranged a private jet to fly him to Montana.

“So, that was fine,” Duffy told the podcast.

Duffy was married to ballet dancer Carlyn Rosser, whom he wed in 1974, and they shared two sons, Padraic and Conor, at the time of the family tragedy.

Before leaving for Montana, he told Padraic and Conor that their grandparents had been murdered.

“They were getting up to go to school,” he recalled. “And I said to the boys, I said, ‘Padraic, Conor, we have to go in now. I’m going to chant with you.’”

Duffy had been practicing Buddhism for 15 years, and chanting was already part of the family’s morning routine.

“I said, ‘We have to chant for Grandma and Grandpa because they’ve both been killed and we have to chant for them because they’re going to understand it and hear,’” he remembered telling his sons.

“And they went, ‘OK.’”

The actor said his Buddhist practice helped him make sense of the loss.

“The Buddhist philosophy is one of continuous life cycle of your entity, for the lack of a better word,” he explained. “But I didn’t study that at all. I was just chanting because it felt good. It felt right. It made my life feel better.”

Duffy built a decades-long career in Hollywood, becoming a household name through his roles on “Dallas,” “Step by Step” and “The Bold and the Beautiful.”