PRINCETON — A former college soccer star from Princeton, New Jersey, has been charged with murdering his little brother — and a pet cat — over the weekend in an apartment near the campus of Princeton University.

Authorities say Matthew Hertgen, 31, allegedly used a knife and a golf club to slash and beat his 26-year-old brother, Joseph Hertgen, to death at about 11:15 p.m. Saturday, according to court docs.

Cops went to the four-story, high-end Michelle Mews apartment complex off Witherspoon Street after Matthew Hertgen called 911 to report a fire and dead body in the apartment, docs said.

When officers arrived, they found Joseph’s bloodied corpse — and quickly pinned the killing on his sibling.

“The complaint alleges that Matthew purposely or knowingly engaged in conduct that led to the death of his younger brother and caused the death of a cat that was located within the residence,” the Mercer County Prosecutor’s Office said in a statement.

Authorities charged Matthew with first-degree murder, weapons offenses and animal cruelty.

If convicted, he faces up to 30 years to life in prison.

The official cause of death will be determined by an autopsy, the prosecutor’s office added. `

Cops in tony Princeton handled the killing as discreetly as possible, according to neighbors — and few said they even knew what had happened before the news stories broke. 

A young mom told The Post on Monday that she saw a line of unmarked police cars parked before the building Sunday morning and thought it meant someone famous was in town.

“I thought maybe … they were keeping an eye on things,” she said. “Then my husband sent me a news article and I couldn’t believe it. Here? You see how quiet this place is. Look around — it’s like never ever happened.”  

Michelle Mews includes both rental units and condos — which can fetch around $2 million — right in the heart of Princeton near campus.

Both brothers were once standout soccer players at Toms River North High School and played in college: Joseph for the University of Michigan, and Matthew for exclusive Wesleyan University in Connecticut.

In high school, Joseph made the all-state team in 2015 and was twice named offensive player of the year and MVP.

At Michigan, he was a three-time Academic All-Big Ten who played in two games as a junior after an injury sidelined him during his sophomore campaign, according to his college athletic profile.

He graduated with a bachelor’s in finance and accounting from Michigan University’s Stephen M. Ross business school, then worked as an analyst with Red Bank, NJ-based asset management firm Locust Point Capital, the company website said.

Before that, he worked for Trimont Real Estate Advisors in Dallas.

Aside from a few traffic tickets and a February 2017 drunk driving arrest, his brother Matthew rarely got in trouble.

Seven months after the DUI, Matthew lost his license for three months and paid about $1,000 in fines, according to online court records.

Another neighbor in Princeton said the whole case sounded like a plot for a “Dateline” episode about wealthy white kids murdering each other.

“This is the town — things happen, then you hear nothing about it,” she said. “They don’t like bad publicity and they’re good at keeping things quiet.”

Her husband added that a number of the pricey units are empty because buyers can pick up big pieces of property a few blocks over for the same price.