Conan O’Brien smiles as he is seen almost one month after hosting Reiners night before grisly murders

Conan O’Brien has been seen after hosting a December holiday party which was attended by director Rob Reiner and his son Nick.

The bash took place on December 13, just hours before Reiner and his wife Michele were murdered allegedly by Nick inside their Los Angeles home.

The talk show host looked to be in good spirts as he posed with fellow comedians such as Tig Notaro, Stephanie Allynne, Jason Bateman, Will Arnett and Alex Edelman on Saturday.

He was attending SiriusXM Presents Before The Buzz at Max & Helen’s.

The star wore a brown jacket over a blue hoodie and blue denim jeans. He added brown-tinted sunglasses that hid his eyes before he entered the venue.

Last month Daily Mail reported exclusively that O’Brien stopped a friend from calling 911 during an explosive fight between Rob and Nick at the comedian’s Christmas party – just hours before the director’s son allegedly cut his parents’ throats, guests have revealed. 

Multiple attendees have reported witnessing Rob, 78, and wife Michele, 70, having a heated argument with 32-year-old Nick at O’Brien’s Los Angeles mansion. 

Nick is said to have been behaving erratically all evening, but one source familiar with the party has now told the Daily Mail the spat grew so intense that at least one guest suggested calling the cops to intervene. 

‘They got in an argument, the father and son. It got so bad and loud someone wanted to call the police to report it,’ the insider claimed.

‘But Conan stepped in and said, “It’s my house, my party, I’m not calling the police.” He talked them out of calling the police.’

O’Brien, 62, did not respond to the Daily Mail’s requests for comment. 

Another source corroborated the account, saying party guests had raised concerns about Nick’s mental state and suggested contacting the cops before O’Brien shut the idea down. 

‘When the s**t was hitting the fan, somebody said we need to call the police. The conversation was about getting this kid put into a mental-health hold,’ the second source told the Daily Mail. 

‘Conan O’Brien stepped in and said, “No, I don’t want the police at my house”. It makes sense; who wants the cops showing up creating a scene?’ the insider added.

‘But the argument between Rob and Nick was pretty intense.’

A source close to the Los Angeles Police Department said there were no 911 calls from O’Brien’s house that night.

And despite partygoers’ concerns, nobody predicted what would happen next: that Rob and Michele Reiner would be found dead from knife wounds less than 24 hours later.

‘Only the murderer is responsible,’ the first source said. 

‘But it must be gut-wrenching for Conan to learn that this is how things turned out. I’m sure that night is replaying for him over and over.

‘It’s just so awful and sad.’

In another haunting revelation, the Daily Mail has also learned that Rob had confided to friends at the O’Brien party about being scared of his own son. 

‘I’m petrified of him. I can’t believe I’m going to say this but I’m afraid of my son. I think my own son can hurt me,’ Reiner allegedly said immediately after his altercation with Nick.

Those comments resurfaced at an impromptu memorial attended by Hollywood A-listers, where the details of the party were discussed, according to a source.

The insider told the Daily Mail that several attendees were left in tears upon hearing what Rob had said.

The Daily Mail contacted representatives for all the stars in attendance at the impromptu memorial. One spokesman denied that Rob had made the comments about Nick at O’Brien’s party.

TMZ first reported that Reiner had had a ‘very loud argument’ with his son at the holiday party, after which the legendary movie director and his wife left.

The Reiners had reportedly brought Nick to the star-studded event to ‘keep an eye on him.’