You’ve only been told half the story about the Reiner murders. These hidden horrors MUST be outed… before Hollywood’s sick secrecy pact wins: MAUREEN CALLAHAN

As we learn more about the Reiner murders, one crucial event remains a mystery: What really happened at Conan O’Brien’s holiday party?

We’ve been told only a little about the before, the during, and the circumstances of Rob, Michele and Nick Reiner leaving in humiliation.

This celeb-studded party is, quite possibly, most crucial in the timeline — the inciting event that may have led Nick to allegedly murder his mother and father in their beds, stabbing them multiple times and slitting both their throats.

So why have we not heard from O’Brien, or any of his party guests, or from law enforcement, the tick-tock of that evening?

Why don’t we know how frequently this 32-year-old unemployed, reportedly schizophrenic drug addict was the perpetual, uninvited plus-one at any number of industry parties and events?

Surely this was not the first time. Surely Rob’s Hollywood pals knew Nick was dangerous.

An insider told the Daily Mail that at least one guest wanted to call 911 during an explosive fight between Rob and Nick at the party.

Another source corroborated that account, claiming that O’Brien shut it down — no calling the police, no trying to get Nick placed in an emergency psych hold.

Imagine how combustive that fight must have been.

‘Conan stepped in and said, “It’s my house, my party, I’m not calling the police”.’

Wow.

O’Brien hasn’t returned requests for comment. Now that’s Hollywood entitlement.

What we do know is telling: Nick Reiner was reportedly not invited to O’Brien’s party, thrown last Saturday night at the talk show host’s Brentwood home.

But Rob and Michele asked if they could bring their deeply troubled son anyway – and it seems O’Brien felt compelled to say yes.

Imagine what O’Brien and his guests, among them Jane Fonda, Larry David, Bill Hader, Billy Crystal — longtime family friend of the Reiners — thought when Nick entered the room with his parents.

One imagines sighs, rolled eyes and a collective, unspoken thought: This guy again?

For Nick was well known in Hollywood for being a jobless, unrelenting, hardcore drug addict who’d turfed through at least 18 rehabs in his short life.

He was known for having rage explosions and for once destroying his parent’s guesthouse, where he was still living, in a cocaine-fueled rage.

Nick bragged about that last one.

In a 2018 interview on the ‘Dopey’ podcast, Nick spoke of violently smashing up the guesthouse after his parents, he said, ‘told me I had to go’.

Rob and Michele, apparently, had tried everything: Tough love, rehab, family therapy and, most recently, a kind of helicopter parenting that saw them too afraid to leave their grown son in their own guesthouse, unsupervised.

A son who, according to TMZ, is also schizophrenic.

That diagnosis will doubtless be played for sympathy in court by his lawyer, top defense attorney Alan Jackson. And it will doubtless result in a plea of not guilty by reason of insanity.

Details about Nick’s medications have begun making their way into the media.

On Friday, and again from TMZ, we learned that Nick had been under a psychiatrist’s care in recent months and that his meds had been switched up, making him ‘erratic and dangerous’ weeks before the murders.

But Nick was erratic and dangerous long before that. One friend recounted seeing Rob restrain his enraged son in a bear hold when Nick was only 11.

And the Reiner murders seem both premeditated — Nick allegedly waiting until his parents were in bed before attacking them — and eerily calm.

If this accused killer was so out of his mind, why was caught on video peacefully walking away from the crime scene? Or buying a refreshment at a gas station?

If he was so out of his mind, why did he check into a Santa Monica hotel and allegedly leave the shower covered in blood?

Someone can be mentally ill and also a cold-blooded killer.

Nick, on destroying that guesthouse years ago: ‘I got totally spun out on uppers — I think it was coke and something else — and I was up for days on end.’

Imagine: Awake and smashing up his parent’s guesthouse for days on end.

What were his parents doing? Why weren’t the cops called then? Or an ambulance?

Nick continued: ‘I started punching out different things in my guest house’ starting ‘with the TV and then I went over to the lamp. Everything in the house got wrecked.’

You can’t tell me that many of the friends at O’Brien’s party knew nothing of this behavior. Nick talked about it on a podcast.

In recent years, photos and videos of Nick — interviews he did with his own father — evoke nothing but alarm, if not horror.

He has a truly psychotic look in his eyes. His affect is way off. He seems hostile towards his father, who had made a movie about his son (which Nick allegedly co-wrote) and who did nothing but effusively sing Nick’s praises.

Back to that party: According to The Hollywood Reporter, Nick — an imposing figure at 6’3″, 230 pounds and with those crazy eyes — began barging around the room and asking multiple people, ‘Are you famous?’

When Nick tried to insert himself into a discussion comedian Bill Hader was having, Hader reportedly informed Nick that he was interrupting a private conversation.

Nick reportedly glared for several seconds before storming off.

Sometime later — again, the timeline is still unclear — Rob and Nick are said to have started arguing loudly, shouting to the point that the whole party was disrupted.

Within minutes, Rob and Michele left the party, but not before Rob, according to an impeccable source, told friends that he was ‘petrified’ of Nick.

‘I can’t believe I’m going to say this, but I’m afraid of my son,’ Reiner allegedly said. ‘I think my own son can hurt me.’

When and how Nick left the party remains unclear. Was he alone or with his parents?

Reports are that Nick doesn’t drive. Did he Uber? Or walk – the nearly 2 miles back to the Reiner family home?

What happened at the O’Brien party needs its own investigation, and the details should be public — because Nick Reiner seems to have been as much a public threat as a private one.

And Hollywood secrecy will only make this worse.