A Bronx courtroom just delivered a gut punch to every cop in New York — and a warning to every law-abiding citizen.

In a ruling that will echo far beyond the borough, Judge Guy Mitchell slammed NYPD Sgt. Erik Duran with a staggering 3-to-9-year prison sentence. His “crime”? Doing his job.

The message couldn’t be clearer: hesitate, stand down — or risk prison.

Duran was convicted of manslaughter after throwing a drink cooler at fleeing suspect Eric Duprey, who crashed and later died. A tragic outcome, yes — but a far cry from the kind of violent intent that usually lands someone behind bars for nearly a decade.

“Today will be forever remembered as one of the darkest days in the history of our profession,” said Sergeants Benevolent Association President Vincent Vallelong. Even former NYPD Commissioner Ray Kelly blasted the ruling as “a huge miscarriage of justice.”

They’re right.

If anything, the case screamed for leniency — not a hammer. Mitchell had the discretion to reduce the charge to criminally negligent homicide, which could’ve meant probation. Instead, he chose to make an example out of a 15-year veteran with no prior record. Why? The judge claimed the sentence would act as a “general deterrent.” Deterrent to what — policing?

Duran was in the middle of a “buy-and-bust” operation, trying to stop a suspect speeding off on a scooter — a potential threat to officers and civilians alike. According to his sworn testimony, he acted to protect fellow cops in harm’s way.

Yet the court twisted that into motive, suggesting he acted just to avoid losing an arrest. So what’s the new rule — let suspects flee? Let chaos reign?

This wasn’t justice. It was a warning shot — aimed squarely at every officer in uniform. And the double standard is glaring.

Back in 2016, Officer Peter Liang was convicted of manslaughter in the fatal shooting of Akai Gurley — and received probation plus community service. No prison time.

Even more stunning: Judge Mitchell himself once handed a gang member just nine months for beating a homeless man to death — despite prosecutors pushing for a decade behind bars.

A cop trying to stop a fleeing suspect gets years in prison. A killer gets months.

And hovering over it all is the aggressive prosecution by Attorney General Letitia James, whose office pushed the manslaughter charge in the first place — and a political climate shaped by Mayor Zohran Mamdani that many in law enforcement say is openly hostile to policing.

The result? Don’t be surprised when cops start walking away from the job in droves — or when fewer arrests lead to more criminals on the street.

When officers are punished for split-second decisions in dangerous situations, hesitation becomes the norm. And hesitation gets people hurt.

An appellate court needs to step in — fast — and overturn this wildly excessive sentence. Because right now, the only thing being “deterred” in New York City is policing itself.