Conan O'Brien 'Wracked With Guilt' After Witnessing Rob Reiner's Heated Argument With His Alleged Killer Son

Conan O'Brien regrets not stepping in during the heated argument Rob Reiner and his wife, Michele, had with their son Nick at his Christmas party last week.

The TV icon reportedly believes that stepping in may have prevented the eventual death of the duo, who were found stabbed at their Brentwood home 24 hours after the party.

The couple's son was arrested shortly after the bodies were discovered and has been charged with two counts of first-degree murder. Nick Reiner made his first court appearance on Wednesday, and his arraignment is set for early next month.

Conan O'Brien Feels 'Guilty' After The Murders Of His Pals, Rob And Michele Reiner

In the wake of Reiner and his wife's shocking murders, O'Brien, who last saw them at his Christmas party just 24 hours before the incident, is said to be privately battling intense guilt over their deaths.

According to reports, the TV icon has been reflecting on those moments in recent days, especially being one of the witnesses who saw the couple have a "very loud" argument with their son, Nick.

"He keeps thinking, 'What if I had stepped in? What if I'd pulled Rob aside or shut it down?" an insider told Rob Shutter's #ShutterScoop. "He feels like maybe he could have changed the course of what happened."

"Conan is replaying every detail in his mind," a second source said about O'Brien. "He's wracked with guilt and keeps wondering if anything he did—or didn't do—could have made a difference."

The Reiners' Son Has Been Charged With Two Counts Of First-Degree Murder

Barely 24 hours after the party hosted by O'Brien, the Reiners were found in their Brentwood home with stab wounds.

Authorities described the incident as a homicide after launching an investigation. Nick was arrested and charged with the double murder of his parents.

He is being held without bail and made his first court appearance on Wednesday, where he waived his rights.

His arraignment was later set for January 7, when he may enter a plea regarding the two counts of first-degree murder against him. He may also make an argument for bail at that time, although it remains unclear whether he will request it.

He is currently being represented by attorney Alan Jackson, who has previously represented figures such as actor Kevin Spacey and film producer-turned-sex offender Harvey Weinstein.

Nick Reiner May Face The Death Penalty If Convicted

If Nick is ultimately found guilty of the murder of his parents, he could face the death penalty.

This was made known by Los Angeles County District Attorney Nathan Hochman during a press conference earlier in the week on the murders.

"[Nick's] charges will be two counts of first-degree murder with a special circumstance of multiple murders," Hochman revealed at the time, per Fox News. "He also faces a special allegation that he personally used a dangerous and deadly weapon, that being a knife. These charges carry a maximum sentence of life in prison without the possibility of parole or the death penalty.

Elsewhere in the press conference, Hochman also revealed that his team will take the "thoughts and desires of the family into consideration" during sentencing. However, this will also depend on "the strength of the evidence, aggravating and mitigating circumstances, and broader policy considerations."

Rob Reiner's Other Children Described Their Death As A 'Devastating Loss'

As tributes continue pouring in and the investigation into the murders of the Reiners remains ongoing, their other daughter and son, Romy and Jake, have recently broken their silence on the incident.

In a statement obtained by NBC News, the duo said they are at a loss for words to describe the "unimaginable pain" they are currently feeling.

"The horrific and devastating loss of our parents, Rob and Michele Reiner, is something that no one should ever experience. They weren't just our parents; they were our best friends," they added, per The Blast.

They also expressed appreciation for the condolences they have received and ended their statement by requesting privacy, without mentioning Nick.

"We now ask for respect and privacy, for speculation to be tempered with compassion and humanity, and for our parents to be remembered for the incredible lives they lived and the love they gave."

Rob Reiner And His Wife Were Worried About His Son's 'Deteriorating' Mental Health

Since their gruesome murder, friends of the Reiners have stressed how much they tried to help their son Nick with his substance abuse and mental health issues.

According to the New York Post, a close family source shared that the actor and his wife were worried that their son was still using drugs and his mental health was declining due to his addiction.

"Rob had been telling people that they're scared for Nick and scared that his mental state was deteriorating," the insider, who is a family friend, told the news outlet. "These poor people did everything to help this kid."

The late couple reportedly sent Nick to multiple rehabilitation facilities, hoping he would beat his addiction.