Speaking with CNN's Chris Cuomo for HLN's "The Menendez Brothers: Murder in Beverly Hills," Lyle detailed the exact moments he and his brother Erik murdered their parents with a shotgun back in 1989.
"That part of it is obviously traumatic and difficult, I can't really parse, it was chaotic," he said of entering his mother and father's room the night of the killings. "It was a dark room and my father was standing ... just a deafening, horrific few moments of my life that come back to me all the time."
"I didn't know what was going to happen in the room," he said. "We definitely fired the instant we entered the room and I think that's part of the reason the police were saying the crime scene was so chaotic. A tremendous amount of shots were fired all over the room, so it was a horrific experience."
The brothers fired somewhere around 15 blasts from their 12-gauge shotguns, brutally killing Jose and Kitty Menendez.
When asked why they fired so many shots, targeting both parents not just their father, Lyle blamed "panic."
"Once you're in a panic, enraged panic ... once you're in that place, you end up using every shell you have and firing way more than you need to," he explained. "I think I would have kept firing until I didn't have anything left to fire, I was just in that place."
During highly-publicized trial, Lyle and Erik alleged they were molested by their father for years.
"You have to understand, my father was a very successful media executive, very high profile media executive. There was no way he was going to go through a child molestation trial," Lyle told Cuomo. The guns were already in the house, they were there in case something happened in the house."
In a separate interview with ABC, Lyle also called his father a "force of nature."
"My father was like a force of nature and you look up to that. You were expected to which be competitive to a fault," he added. "He began to sort of try to groom me to be hypercompetitive and succeed."
Lyle and Erik are both serving life sentences without any chance of parole. The brother play chess through the mail and have "almost never talked" about the murders.