Jake Reiner — whose parents, prolific filmmaker Rob Reiner and Michele Singer Reiner, were killed late last year, and whose younger brother has since been charged with their murders — spoke out Friday about the “living nightmare” he has endured since learning what happened to them.

Reiner, 34, wrote on Substack that on Dec. 14 he was attending a celebration of life for a friend who had died in October when his sister, Romy, called to tell him their father was dead. Minutes later, she called again: their mother was gone, too.

“My world, as I knew it, had collapsed. I was in a trance,” Reiner wrote. The only thing I could focus on was that I needed to get to my childhood home. I needed to get to my sister. I needed to figure out what the hell just happened.”

He wrote that he was “robbed of so many things that day.”

“My parents won’t be at my wedding, they won’t get to hold their future grandchild, and they won’t get to see me have the successful career I’m still seeking,” he wrote. “It simultaneously breaks my heart and enrages me.”

Rob Reiner, 78, and Michele Singer Reiner, 70, were found dead in the primary bedroom of their Brentwood home on Dec. 14 by paramedics responding to a call, officials have said.

Nick Reiner, the couple’s middle child and youngest son, was arrested the same day about 15 miles from the home. He has been charged with two counts of murder with the special circumstance allegation of multiple murders. He also faces a special allegation that he used a deadly weapon, a knife. He has pleaded not guilty.

Jake Reiner wrote that “nothing can prepare you for what it feels like to lose both parents instantly at the same time.”

“It’s too devastating to comprehend. I still wake up every morning having to convince myself that, no, it’s not a dream,” he wrote. “This truly is my living nightmare.”

He said he keeps thinking about how frightened his parents must have been and how they were the “last people in the world to deserve what happened to them.”

“They should be enjoying the rest of their lives peacefully while growing older together. Instead, that was ripped away from them, from me, from Romy, and there was nothing we could do about it,” he wrote.

Reiner said his sister would share her own experiences and reflectons about her family in her time.

He described his parents as “the center of his life” and his “guiding lights, the foundation of who I am as a human being, and the most giving people I have ever known.”

“A lot of people don’t have the luxury of having the best parents, the best mom, or the best dad, but I did,” he wrote. “The love they have for me, my brother, and my sister is truly unconditional.”

Reiner did not name his younger brother in the post, but wrote that “we lost more than half of our family that night in the most violent way imaginable.”

“Sure, any loss of a parent is devastating, but nothing compares to losing both of them at the same time and, on top of that, having your brother be at the center of it. It’s almost too impossible to process,” he wrote.

He acknowledged that the public has questions about what happened, but said some answers would come in time — and that some details belong only to the family.

“Keeping them private is the only way to protect what little remains of something that was taken from us,” he wrote.

Reiner closed with a plea for understanding. “What the hell do you say to someone who is living through this reality?,” he wrote. “The truth is, there is nothing to say. I just ask for love and compassion — the same principles my parents lived by.”