Blood allegedly found in hotel room Nick Reiner checked into hours after arguing with father Rob Reiner

Blood allegedly was found in a hotel room Nick Reiner checked into hours after arguing with his famed moviemaker father, Rob Reiner, at Conan O'Brien's Christmas party, TMZ reported.

Nick Reiner, 32, is in custody with no bail after police said he killed Rob Reiner and his wife, Michele Singer Reiner.

When hotel staff entered Nick Reiner's room later on Sunday morning, they found the shower 'full of blood' and blood on the bed, TMZ reported.

The night before the Reiners were found stabbed to death in their Brentwood, California, home, Nick Reiner's behavior alarmed guests at the party, New York Times reported, citing two attendees who asked not to be named in order to maintain relationships.

More from the Times:

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 behavior 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 recognized 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 behavior, saying he looked anxious and uncomfortable in a way that deeply unsettled them.

Representatives for O’Brien declined to comment Monday, the Times said.

RELATED: Hollywood icon Rob Reiner, wife found dead in their home; police are calling it a homicide (UPDATE)

Nick Reiner used his credit card to check into the Pierside Santa Monica hotel around 4 a.m. Sunday — just hours after his argument with his father — TMZ reported, citing sources with direct knowledge.

Eyewitnesses who saw Nick Reiner check in to the hotel told TMZ he seemed "tweaked out," but there were no visible signs that he had been in a violent confrontation and there were no bloodstains or cuts on his body.

TMZ added that Nick Reiner's reservation was for one day, but he never formally checked out.

When hotel staff entered Nick Reiner's room later on Sunday morning, they found the shower "full of blood" and blood on the bed, TMZ reported, adding that room's window was covered by bedsheets.

LAPD Robbery-Homicide detectives went to the hotel Monday to gather evidence and interview employees, TMZ said, adding that Nick Reiner was located and arrested about 20 miles away in Exposition Park, near downtown Los Angeles.

Reiner was arrested around 9:15 p.m. Sunday night; authorities were called for medical aid to the Reiner home around 3:30 p.m. Sunday, where the bodies of his parents were found.

Fox News in its video report said Nick Reiner is on suicide watch.

Like Blaze News? Bypass the censors, sign up for our newsletters, and get stories like this direct to your inbox. Sign up here!