Article continues below advertisementRob Reiner and his son Nick were involved in a heated altercation at Conan O'Brien's Christmas party on Saturday night, December 13 - just hours before the famous film director and his wife Michele Singer Reiner, were found murdered inside of their Los Angeles home.The Princess Bride director got into a "very loud argument" at the A-list bash, with their amplified conversation being vocalized enough for other guests to hear, family sources revealed to TMZ shortly after Nick was arrested in connection with his parents' brutal killings.