The shocking story has gone viral: A passenger boarded a United Airlines flight from Houston to New York with her two children and her 10-month-old French bulldog, Kokito.

Despite Kokito being in a TSA-compliant carrier, there was an issue with fitting the carrier under the seat as required. The flight attendant took the carrier and placed it in the overhead compartment.

Kokito was dead before the flight landed at LaGuardia Airport.

How could this happen?

The flight attendant is claiming she wasn’t aware there was a dog in the carrier, but this is implausible. The dog’s owner and her 11-year old daughter insist they informed the attendant and witnesses support their account, and even say the dog was barking.

But all of that is beside the point. How did the family, the witnesses or anyone working on that flight allow this insane act to take place?

No one wants to blame the victim. The family is obviously traumatized and many on the flight with them have posted distraught comments on social media about what happened.

But something is deeply wrong here: No one did anything to stop the stewardess.

One person uncritically following an authority figure is understandable. A plane full of people doing the same is terrifying.

This incident doesn’t exist in a vacuum. When someone goes to put a dog into an overhead compartment, there should be a chorus of voices to say it’s a bad idea — and stop them if they persist. That there wasn’t is a bad sign for our society.

A passenger sitting behind the family posted on her Facebook page that “They INSISTED that the puppy be locked up for three hours without any kind of airflow. They assured the safety of the family’s pet so wearily, the mother agreed.”

Her use of “they” implies that more than one United employee on the plane was involved in this terrible tragedy.

The dog allegedly barked for two hours, then stopped. The family wanted to check on the dog but because of turbulence were told to stay in their seats. They followed the rules at all cost.

There have been many stories in the last few years of cases of horrific abuse and “MeToo” stories that went on while people were aware it was happening. Our news reports often have accounts of robberies that happen while groups of people watch or bullying that happens while school administrators are aware of it.

There is some risk to getting involved, of course — and too many people are choosing not to take that risk. The situation on the United flight wasn’t as dangerous as stepping in to stop a robbery or reporting a rape. Yet still no one spoke up.

While United Airlines should ultimately be held accountable, there are many people who could have, and should have, acted along the way.

Other passengers will say they were just following official instructions and no one wanted to cause a scene. But the implications of that are much worse than just listening to the bad instructions of a flight attendant.

The famous 1960s Milgram study found that people would blindly obey orders from an authority, even when that order was to torture someone for seemingly no reason. Yale researcher Stanley Milgram sought to explain how atrocities like the Holocaust occur and found that many people will simply do what they’re told.

It doesn’t have to be an unquestionably sinister or illegal situation like the abuse of children or torture that should spur us to action. It could simply be someone doing something dangerously stupid, like stuffing a dog into an overhead compartment while people nearby read the newspaper and ignore the barking.

An old episode of “The Office” features Michael unquestionably following his GPS and driving into a lake. “The machine knows,” he screams as his friend tries to stop him. But machines are fallible, as are humans — and unthinkingly following either can end with our cars in lakes and our dogs dead in the airplane overhead.

Stepping in on behalf of others should become something we routinely do. If you find yourself in a situation where you’re thinking “somebody should do something,” make that somebody you, and teach your children to become the type of people who would do the same.

It isn’t enough to “see something, say something.” We must feel obligated to do something.

This column originally appeared in the New York Post.