Rob Reiner is said to have argued with his son at a party night before murder

The night before Rob Reiner and his wife, Michele, were found dead, their son, Nick Reiner, attended a holiday party with his father at the home of Conan O'Brien and alarmed the guests with his behaviour, according to two attendees who asked not to be named to maintain relationships.Rob and Nick Reiner got into a shouting match at the party in West Los Angeles, said one of the attendees, who recalled Rob Reiner telling his son that his behaviour was inappropriate. The attendee, who did not speak to the Reiners at the party, said that people seemed to be very aware of Nick Reiner's history with drug abuse, which the family has discussed publicly.Another attendee said that he did not witness the dispute, but he recognised Rob Reiner in the crowd and noticed the younger Reiner hovering at the fringes of the informal gathering.

The guest said that he and other attendees were worried and that several people commented to him on Nick Reiner's behaviour, saying he looked anxious and uncomfortable in a way that deeply unsettled them. A third person who attended the party said that he saw the Reiners but did not see the argument.

Representatives for O'Brien declined to comment on Monday.Nick Reiner, 32, was arrested Sunday night, hours after Rob Reiner and Michele Singer Reiner were found stabbed to death in their home in the affluent Los Angeles neighbourhood of Brentwood.

Los Angeles authorities said the son was being held without bail at the city's Twin Towers Correctional Facility.The couple - a renowned actor, director and liberal political activist and an accomplished producer - had three grown children together and were well known to their neighbours, as well as to California's entertainment and political circles. Neighbours and acquaintances said that Nick Reiner's struggles with drugs and alcohol were common knowledge in the affluent West Los Angeles enclave.In 2016, the father and son released a semi-autobiographical film, "Being Charlie," about a Los Angeles teen who abused drugs and who had a turbulent relationship with his father. At the time, Nick Reiner was 22 and said he had been in and out of rehab about 18 times since he was 15.