Nick Reiner, the son of legendary director Rob Reiner and Michele Singer Reiner, pleaded not guilty to two counts of first-degree murder in connection with their deaths in a downtown Los Angeles courtroom for his arraignment on Monday (February 23), Page Six reports.

Reiner made his first appearance in a Los Angeles courthouse on December 17 after being charged with two counts of murder in connection with his parents' deaths. Rob and Michele Reiner allegedly got into a "very loud argument" with their son at comedian Conan O'Brien's party, which led to them leaving, prior to their deaths on December 14.

A source had previously told PEOPLE that Nick Reiner was acting erratically at the party.

“Nick was freaking everyone out, acting crazy, kept asking people if they were famous,” an insider told PEOPLE.

Nick had publicly acknowledged his issues with drug addition and homelessness in the past. Rob and Michele Reiner were reported to also have stab wounds to multiple other parts of their bodies, sources with knowledge of the situation confirmed to the New York Post.

Rob Reiner, the son of producer, writer and actor Carl Reiner and actress and singer Estelle Reiner, initially gained national prominence playing Mike 'Meathead' Stivic on All in the Family and is credit with numerous acting roles during a career that spanned seven decades. The New York City native made his directorial debut with the heavy metal mockumentary This Is Spinal Tap (1984) -- having released a sequel earlier this year -- which was followed up by The Sure Thing (1985), Stand By Me (1986), The Princess Bride (1987), When Harry Met Sally...(1989), Misery (1990) and A Few Good Men (1992).