A Houston police sergeant was charged with murder after allegedly gunning down his wife, a popular school librarian — because he believed she had been flirting with a family friend, according to authorities and the couple’s daughter.

The pair’s daughter revealed in court documents obtained by ABC 13 that she, her husband and her parents had been drinking at her parents’ Pearland home Saturday night along with a family friend. Her dad, Hilario Hernandez, 56, believed that her mom, Belinda Hernandez, 52, was flirting with the male friend — setting him off, the daughter said.

Later that night, the couple’s daughter became worried when she texted her mom to say she got home safely but her mom didn’t answer. When the daughter then called, her dad answered, reporting that his wife was fine and hung up, the documents said.

The daughter was not convinced, so she and her husband returned to the home — where they found Belinda face-down in the kitchen with multiple gunshot wounds.

Hilario Hernandez, 56, was busted hours later at a Kingsville hotel — about 100 miles north of the Mexican border. Houston police spokeswoman Jodi Silva confirmed to The Houston Chronicle that he was a member of the force.

Belinda Hernandez was a librarian at Shadycrest Elementary, which had extra counselors on hand Monday to help grieving students.

Belinda and Hilario were married for more than 30 years and had two grown children, according to the Chronicle.

Belinda told the paper in a 2014 interview about her burgeoning career in education that she was “very happily married” and “loved my children,” but that she always wished she’d gone to college to become a teacher.

A longtime family friend told ABC 13 that she had just hugged the librarian at the school Friday.

“Gave her a hug and you would have never known that anything was wrong, she seemed happy,” the friend recalled.

She also called Hilario “absolutely a good dad.”

Police are searching for surveillance video that could provide more details about the case, Pearland police spokesman Jason Wells told the Chronicle.

“We are going to conduct business as usual,” he said. “The law is held accountable for everybody, actually more so for [officers].”

Neighbors called the area a quiet suburban neighborhood where violence was uncommon.

“They seemed like just everyday, normal people,” nearby resident Lucretia Jeansonne, 64, told the paper.

A GoFundMe page has been set up to help the couple’s children raise money for their mother’s funeral expenses. By Monday afternoon, it had already raised $9,640 in donations.