The Oscar-winning Three Billboards Outside Ebbing, Missouri was inspired by the 27-year-old slaying of Kathy Page in Vidor, Texas
Credit: Texas Department of Public Safety

The Oscar-winning drama Three Billboards Outside Ebbing, Missouri — starring Frances McDormand as a grief-stricken mother made furious by law enforcement’s failure to solve her daughter’s homicide — was inspired by a 27-year-old murder case in Texas that remains unsolved.

Investigators have now doubled the reward for any information that leads to an arrest in the killing of 34-year-old Kathy Page, PEOPLE confirms.

On May 14, 1991, Page, reportedly a mother and waitress, was found dead inside her car in Vidor, Texas — but her death was no accident, state authorities say.

Page had been strangled and the scene was staged, according to the Texas Department of Public Safety: Her car was nose-down in a ditch 100 yards from her home in an attempt to make it appear she had been in an accident.

Despite evidence of a homicide, no arrests have ever been made in Page’s death.

Vidor Police Chief Rod Carroll tells PEOPLE the case is very much still open and that authorities have always had an unnamed person of interest. Carroll characterized Page’s death as a likely “crime of passion.”

Frustrated by the lack of resolution, however, Page’s father, James Fulton, began putting up billboards along I-10 in the Vidor area.

In 2012, he erected one accusing Page’s estranged husband, Steve Page, of her murder and claiming the Vidor Police Department had taken bribes instead of working to catch the killer, according to the Beaumont Enterprise.

“Steve Page Brutally Murdered his Wife in 1991,” the billboard stated. “Vidor P.D. Does Not Want to Solve This Case. I Believe They Took A Bribe. The Attorney General Should Investigate.”

According to the Enterprise, other billboards that Fulton has put up include “Vidor Police Botched Up the Case,” “Waiting For Confession” and “This Could Happen To You!”

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Kathy and Steve were recently separated at the time of her death, according to DPS. Chief Carroll says that Steve declined to cooperate with police during their investigation.

Though police say Steve has never been charged in Kathy’s death, a civil jury found Steve liable in a wrongful death suit brought by Fulton, according to a later appellate decision in the case reviewed by PEOPLE.

The civil jury “found Steven Page killed Kathy Page,” according to court documents reviewed by PEOPLE. (In a civil trial, a jury need only find it more likely than not that the defendant is responsible — while in a criminal proceeding, the jury must find guilt beyond a reasonable doubt.)

Kathy’s family was awarded $150,000 in the suit.

According to court documents, a detective testified during the civil trial that when police informed Steve his wife was dead, he “became emotional, throwing himself on the couch and crying, but in the light of his flashlight [authorities] noticed that Steve had no tears at all.”

Grand juries have declined to indict Steve in Kathy’s death, the Enterprise reports.

“The investigation never closed,” Chief Carroll told the paper earlier this year. “There has always been a person of interest. We need evidence for probable cause. Sometime, someone will grow a conscience and come forward. It’s the human psyche.”

The state DPS could not be reached for further comment. Steve, whom authorities say lives in the Houston area, could not be reached directly.

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Three Billboards Outside Ebbing, Missouri
| Credit: Merrick Morton/Fox Searchlight Pictures

Fulton’s messages inspired U.K. writer-director Martin McDonagh to make Three Billboards Outside Ebbing, Missouri, according to the Houston Chronicle. McDonagh said he saw some of the signs in Vidor during a road trip years ago, the paper reports.

“I really do hope that because of all this press attention because of the film that something might shift in the case, that some kind of justice might finally be served,” McDonagh told the Chronicle. “In fact, that would be the most important thing to come out of this movie.”

The original reward of $3,000 has been increased to $6,000, according to DPS.

“The movie brought this case back to life,” Carroll, who only fairly recently became police chief, told the Chronicle in March.

Carroll said he wasn’t bothered by the billboards but that witnesses to what happened will be key to moving the case forward.

McDonagh’s reps could not be reached for comment Thursday.

“This is a bigger story than that,” Fulton said in an interview with the Chronicle, noting that he had not been in contact with the Three Billboards filmmakers and had not seen the film. “My story is.”

“This is my priority until my death, to try to get something done,” he told the paper. “It’s not over with yet. No. I’m fixing to do a whole lot more than what I’ve already done.”