NICK REINER’S FINAL ACT AFTER MURDERING ROB AND MICHELE’S PARENTS: “” AT A LUXURY HOTEL WITH STUNNING OCEAN VIEWS AFTER A “BLOODY PARTY’

LOS ANGELES — Nepo-baby junkie Nick Reiner checked into a trendy beach hotel with an indoor fire pit and sweeping views of bougie Santa Monica allegedly after slitting the throats of parents Rob and Michele Reiner.

The privileged accused-killer son of the legendary Hollywood director was in enough of a frame of mind to find his way to the Pierside Hotel, just steps from the tony California town’s iconic pier, in the pre-dawn hours of Dec. 14 — sometime after law-enforcement sources say he is believed to have killed his parents in their Los Angeles mansion roughly 5 miles away.

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Nick, 32, would have strolled past the hotel lobby’s quaint Christmas tree, upscale restaurant and cozy fire-pit sitting area featuring wicker chairs to get to the check-in desk to rent a $300-a-night room at the primely located lodging between the pier and a light-rail station — which has a line leading directly to the location where he was arrested later that night.

He couldn’t have picked a more public place to hunker down for awhile — although at that time of morning and in the typically teeming area, he wouldn’t have registered on anyone’s radar.

But he was jittery, appearing “tweaked out,” when he arrived, witnesses told TMZ — and thus likely oblivious to the hotel’s features, including its lobby with floor-to-ceiling windows offering a semi-panoramic view of the local area.

The accused murderer’s second-floor room would have also afforded him his own private stunning view of the ritzy seaside enclave — although at some point, he hanged bed sheets over all the windows, blocking the sight, authorities have said.

Law enforcement later blocked off a section of the hallway where Nick’s room was located as the investigation continues, a staff member told The Post.

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After Nick left the hotel sometime that day, never formally checking out, cleaners found the shower and bed in his room covered in blood. But witnesses noted that Nick had no visible blood on him when he walked in, according to TMZ.

The deeply disturbed son is accused of killing his icon father, 78, and photographer mother, 70, sometime between an embarrassingly public blow-up the three had at Conan O’Brien’s holiday party Saturday night and when his sister Romy found their parents’ body at the family’s mansion in Brentwood on Sunday afternoon.

Law-enforcement sources have said they believe Nick killed Rob and Michelle between leaving the party and arriving at the hotel.

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He and his parents may have been arguing over Nick’s bizarre behavior with party guests including “SNL” alum Bill Hader and the desperate need for him to go back into rehab.

Security-camera footage then showed him leaving his parents’ house just before midnight, and he was spotted again a short time later calming buying a drink at a nearby gas station.

Four hours later, Nick was checking into the Pierside — a 10-minute drive and roughly a roughly 90-minute walk.

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His movements then throughout the day Sunday are unclear, but around 9 p.m., Nick turned up at another gas station near Exposition Park about 15 miles across town.

Officers arrested him in the street in front of the gas station, video footage shows.

He was placed on suicide watch after his bust, law-enforcement sources have told TMZ, and failed to appear for his scheduled Dec. 16 arraignment because he hadn’t been “medically cleared,” his lawyer said.