Could the murders have been prevented? Guests at Conan O'Brien's Christmas party allegedly wanted to call 911 after witnessing an explosive argument between Rob Reiner and his son Nick Reiner hours before the late film director was murdered - but the comedian reportedly wasn't having it.

In a bombshell report released on Friday, December 19, a source familiar with the A-list bash claimed O'Brien refused to let anyone contact law enforcement following a heated conversation between Rob and Nick, which was allegedly about placing the now-accused murderer in a psychiatric hold.

"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 told Daily Mail. "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 doubled down on the claims, admitting guests became worried about the state of the 32-year-old drug addict's mental health.

MORE ON:Conan O'BrienCops Rush To Blac Chyna's Home After Claims She Was Neglecting Her DaughterDisturbing 911 Call Leaked: Richard Sherman's Wife Says Football Pro Was 'Threatening To Kill Himself' Before ArrestBam Margera Threatened To 'Kill' Man With Brass Knuckles Following Domestic Violence Arrest: ReportWant OK! each day? Sign up here!"When the s--- 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 confidant confessed."It makes sense; who wants the cops showing up creating a scene?" the second source acknowledged, placing blame for the catastrophe away from O'Brien. "But the argument between Rob and Nick was pretty intense."According to various reports, the amplified chat caused Rob and his wife, Michele Singer Reiner, to leave the holiday party early. The When Harry Met Sally director notably only brought Nick to the celebrity gathering in an effort to "keep an eye on him" amid growing worries for his troubled son's well-being, a source told Rolling Stone after Rob and Michele were found dead with their throats slit inside of their Los Angeles home.

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