Conan O'Brien reportedly stopped guests from calling 911 on Nick Reiner at his Christmas Party last weekend. An insider, while speaking to the Daily Mail on Friday, mentioned that O'Brien stopped his party guests from calling the cops. Nick Reiner and his father reportedly got into a heated argument at Conan's Christmas party hours before Rob and his wife were found dead at their Brentwood home.The insider noted,"They got in an argument, the father and son (at the party). It got so bad and loud (that) someone wanted to call the police and report it. 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."A second source who attended the party mentioned that some guests grew concerned that Nick needed to be placed on psychiatric hold due to his behavior."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. It makes sense; who wants the cops showing up creating a scene? But the argument between Rob and Nick was pretty intense."More revelations about Conan O'Brien's Christmas party that Nick Reiner attended emergeAs per the insiders, Rob Reiner reportedly told some of his friends at the party that he was "petrified" his son could "hurt" him. A source who reportedly attended a gathering for Rob and Michele on Monday told Daily Mail that guests were left in tears, after an A-listed recalled the producer director's last words at the party. The celeb quoted Rob's words,"I'm petrified of (Nick). 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."As per TMZ, Nick Reiner allegedly checked into The Pierside Santa Monica hotel around 4 a.m on December 14. The outlet reported that when staff came to check the room, they discovered blood on the bed and in the shower.The couple's bodies were discovered by their daughter, Romy Reiner, on Sunday at their Brentwood home. Rob and Michele Reiner's bodies were discovered with stab wounds to their throats, along with several other wounds throughout their bodies. The Los Angeles County Medical Examiner's Office noted official causes of death as "multiple sharp force injuries."The LAPD released a statement on December 15, mentioning that Nick Reiner was responsible for the couple's deaths.