Rob Reiner & Son Nick in 'Loud Argument' at Conan O’Brien’s Christmas Party on Saturday (Report)

Rob Reiner and his son Nick Reiner reportedly got into a heated argument the night before Rob and his wife Michele Singer Reiner were found dead with their throats slit.

Family sources tell TMZ that Rob and Nick got into a “very loud argument” at Conan O’Brien’s Christmas party.

Afterward, Rob and his wife Michele left the party. It was unknown if Nick left with them.

Nick has since been arrested on a felony charge and is being held by the L.A. County Sheriff’s Department on $4 million bail.

Family sources also told TMZ that Michele had told friends she and Rob were concerned about Nick’s mental health and alleged substance abuse issues, telling others, “We’ve tried everything.”

Heartbreakingly, the beloved couple's bodies were reportedly found by their daughter Romy Reiner, Nick’s sister.

The home, covered in holiday decorations, was immediately sealed off by investigators, but neighbors reported seeing close pals Billy Crystal and Larry David at the home after the news broke. Rob Reiner's assistant Rocco was also on hand to lend assistance as needed.

Nick has long spoken about a battle with substance abuse, and — in spite of his family's wealth — periods of being unhoused.

Nick co-wrote with Matt Elisofon the semi-autobiographical 2015 film "Being Charlie," which his dad directed. He told People at the time, “Now, I’ve been home for a really long time, and I’ve sort of gotten acclimated back to being in L.A. and being around my family."

The well-received film starred Nick Robinson of "Love, Victor"; Cary Elwes, who starred in Rob Reiner's classic "The Princess Bride"; and Common.