Rob and Michele Reiner’s murder: What happened at Conan O’Brien’s party hours before the director and his wife were found dead?

Just hours before Hollywood was stunned by the brutal deaths of director Rob Reiner and his wife, Michele, the family drama had already spilled out into public view — under twinkling lights and cocktail chatter at a celebrity holiday party.

On Saturday night, the Reiners attended a festive gathering hosted by Conan O’Brien, but the cheer reportedly curdled fast.

What happened in party?

At the Conan O’Brien Christmas party, witnesses say a loud, heated argument erupted between Rob, Michele and their son Nick — tense enough to turn heads and quiet the room.

Rob and Michele left after the altercation, but it was not clear when Nick departed. “It’s unclear what the argument was over but it was so heated and so animated, that we are told people at the party overhead the commotion,” said Charlie Neff with TMZ.

Some guests told TMZ that Nick seemed out of place based on his attire and demeanour. He reportedly wore a hoodie while others wore formal suits and dresses, and “he didn’t talk to anybody. He just kept to himself with a blank stare on his face like no emotion. And he didn’t look well,” said an unnamed party-goer.

By the end of the night, Rob and Michele left early. By the next afternoon, they were found dead in their Brentwood home, and Nick would be taken into custody on suspicion of murder.

Rob and Michele were found dead at their home on Sunday, Dec. 14 from apparent stab wounds. Their daughter, 28-year-old Romy Reiner, discovered them and called police.

“She told police that her brother Nick has a history of mental illness as well as substance abuse issues and she felt he was dangerous,” Neff explained. Nick was arrested by the Los Angeles Police Department later that night and booked on suspicion of murder on Monday. He is being held without bail.

Drug addiction, suicide watch: Meet Nick Reiner

Nick has openly shared his struggles with drug addiction and has experienced homelessness. He wrote the film “Being Charlie,” loosely based on his life, which was released in 2015.

The film was directed by his father and won a SAMHSA Voice Award. By the age of 18, he had cycled in and out of nine treatment facilities.

This case marks what could be the fifth incident of patricide in Southern California in recent months.

Nick has reportedly been placed on suicide watch after his arrest for allegedly stabbing the parents to death inside their California home, NY Post reported.

Nick Reiner is currently being held in administrative segregation and on suicide watch while behind bars at Twin Towers Correctional Facility in Los Angeles, law enforcement sources told TMZ.

Last week the son of Grammy-nominated singer Jubilant Sykes was charged with murder. Officials said radiologist Dr Eric Cordes, 63, and his wife Vicki Cordes, 66, were gunned down in their driveway by their son late last month.

In Perris, 47-year-old Juan Gonzalez was arrested on suspicion of killing his 70-year-old father, and in Lake Balboa, 30-year-old Joshua Bonilla allegedly stabbed his father, 62-year-old Elias Bonilla, to death.