A retired firefighter in Mississippi has been charged with murdering his wife of more than 40 years after she had a stroke and he became a “fixture by her side” as she recovered at a rehab facility, police officials said.

Thomas Ballenger, 70, of Clinton, was arrested late Tuesday after police responded to a call at the Woodlands Rehabilitation and Healthcare Center, where Rebecca Ballenger, also 70, was found dead, Clinton Police Department spokesman Mark Jones told The Post.

It’s unclear exactly what Ballenger said after the shooting, but he immediately surrendered to nurses and staff at the facility while admitting that he had just shot his wife multiple times with a revolver, Jones said.

“He was a fixture by her side,” Jones told The Post during an interview early Thursday. “He was a doting husband. He was there by her side caring for her needs, patiently sitting by her side since her stroke.”

Ballenger remains jailed without bail at the Hinds County Detention Center, where he’s being held in a cell outside general population, Jones said.

“He’s in a secluded cell, being monitoring constantly,” Jones said, adding that Ballenger had not made any statements indicating that he wished to harm himself. “We want to take every step we can to protect him.”

Ballenger made his initial court appearance Wednesday and asked for a public defender. Jones said the killing marked the city’s first homicide since April 2014.

“This is the saddest crime I’ve ever worked,” Clinton police Lt. Josh Frazier told the Clarion Ledger.

Frazier said Ballenger’s wife had a stroke and told her husband that she didn’t want to live in a diminished capacity. The couple had been married for more than 40 years and Thomas Ballenger was depressed in the aftermath of his wife’s stroke last month.

There were no reports of an altercation or disagreement between the Ballengers prior to the shooting, WJTV reports.

“They were married,” Frazier told the station. “They were each other’s shadows. They cared for each other a lot. But there is some indication the victim said she did not want to live like that.”

Staffers at the facility are reeling in the aftermath of the fatal shooting, police said.

“They are all in shock,” Frazier told the station. “We spoke to nurses last night. They got to know the Ballengers over the last month. Knew them as good people — both of them. This is a tragic situation for all parties involved.”

Officials from the Jackson Fire Department issued a statement expressing their condolences after the killing.

“To the family of Thomas and Rebecca Ballenger, this family has suffered a great loss,” the statement to WJTV read. “On behalf of Fire Chief Willie G. Owens and the entire Jackson Fire Department, we are so very sorry for your loss. Our condolences and prayers are with the entire family at this time.”