On tomorrow's episode of Dateline, NBC News' Keith Morrison examines the infamous Menendez brothers case. In an exclusive clip obtained by People, Lyle Menendez was sobbing hysterically in a 911 call on Aug. 20, 1989, to report the deaths of his parents, José and Kitty, who had been killed by gunfire. "They shot and killed my parents!" he cried to the dispatcher.

Yet more than two decades after he and his brother, Erik, were convicted of murdering their parents, Lyle said he wasn’t "grief-stricken" on that call, despite his cries. "I think I was just absolutely broken down with stress," he told Keith. "Both of us were just in such a state of trauma and I just — it didn’t pour through on that call," Lyle said. "It made it very easy to make that call, really."

menendez brothers home

Over the years, the brothers — who are currently serving life sentences in two separate California prisons — have opened up in interviews about shooting down Kitty and Jose in their family’s Beverly Hills mansion. This past January, Lyle, 49, told ABC News how he has learned to live with the crime. "I am the kid that did kill his parents, and no river of tears has changed that and no amount of regret has changed it," he said. "I accept that. You are often defined by a few moments of your life, but that’s not who you are in your life, you know. Your life is your totality of it."

Prosecutors said the slayings were part of a larger scheme to get the Menendez parents’ $14 million estate, but the brothers claimed that they acted in self-defense after years of abuse. In Friday's interview, Lyle said their claims have been distorted by authorities. "There are, like, 200 to 300 hundred parricide cases a year, where a parent is killed by a child. And they are almost all related to abuse. And they are almost all settled. This case they picked out as different." he said, "And I think that it was very easy because it was Beverly Hills and my father had a lot of money, to sort of sell this headline that these brothers killed for money."

When Keith asked why he didn't relay that message in his 911 call, Lyle laughed, "I don’t think I was going to tell the Beverly Hills Police Department that I killed my parents and here’s why and they were going to go, ‘Okay, go back home.’"

Unthinkable: The Menendez Murders airs Friday 9 p.m. EST on NBC.

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