When Alison Dupras learned that her mother and grandmother had been found dead in December — both fatally shot at home and left for days — the name of the killer came immediately to mind.
“I know that my father did this, I knew that as soon as I knew what had happened,” Alison tells PEOPLE. “I knew it right away. Right then and there, I knew.”
She even confronted dad Alan Dupras and implored him to turn himself in, but to no avail. “That’s all I wanted was for him to confess, either to me or to the authorities,” Alison says, “and I just knew that wasn’t going to happen.”
Alison was in regular contact with authorities during their months-long investigation and kept up public pressure for an arrest. She reportedly held a protest at the district attorney’s office in late July.
“We are gathering silently and peacefully to let (the district attorney) know that we as a community cannot accept anything other than an arrest and full trial…” she said then, according to the Fresno Bee. “I have been told the detectives are certain of who has committed this atrocity and any jury would find the suspect guilty.”
Alan, 58, never went to the police. But on Sept. 25 — nine months after the double shooting of his estranged wife, retired elementary school principal Jennifer Dupras, 55, and her 88-year-old mother, Cynthia Houk — authorities came to him.
Arrested at his home in Kingsburg, California, Alan faces charges of murder as well as possession of assault weapons, vandalism and two counts of arson.
He has pleaded not guilty and his attorney, Mark Broughton, dismissed the case as “purely circumstantial,” without eyewitnesses, a murder weapon or a confession.
Investigators, however, said they discovered enough proof to believe he was responsible.
• For more on the life and slaying of Jennifer Dupras and her mom and the arrest of Alan Dupras, subscribe now to PEOPLE or pick up this week’s issue, on newsstands Friday.
Speaking to reporters the same day as Alan’s arrest, Fresno County Sheriff Margaret Mims cited “technology and digital data” that helped implicate him as well as evidence “received just this month” that was “needed to confirm that he was in fact the suspect.” Mims also said there was signs the slayings were premeditated.
“We do know that he suspected there was a relationship between Jennifer and another man,” she said of Alan, “and those are the possibilities that we’re looking at as far as motive.”
• Want to keep up with the latest crime coverage? Click here to get breaking crime news, ongoing trial coverage and details of intriguing unsolved cases in the True Crime Newsletter.
A search warrant and supporting affidavit released this summer, before Alan’s arrest, further detailed out a series of allegedly incriminating discoveries in the murder investigation. For example, in December, investigators said they learned from a relative of Alan’s that he drunkenly “bragged” about setting Houk’s car on fire the month before she was killed.
He’d also researched ways to disable the computer in his truck in order to hide its location while driving, the affidavit alleges.
Two Lives Cut Short
The bodies of Jennifer and her mother were found in Houk’s Fresno home on Dec. 11, two days after both had been shot. The homicides — unusual for the area — came just as Jennifer seemed to be getting everything in her life in order.
Having recently retired from a 26-year career in education, she moved in with her mom and filed for divorce from Alan, ending a troubled 26-year marriage.
“She told me she was the happiest she had ever been,” Jennifer’s friend Kelly Rosales tells PEOPLE. “You could see it. I ran into her at a restaurant one night and she had the biggest smile. She was just light. She was just airy.”
Jennifer had even recently started dating again.
“She found someone who was really sweet to her,” her daughter says. “I’m not surprised, because she’s so perfect.”
RELATED: A Burning Car, Burning Building & Double Murder — Unraveling Estranged Husband’s Alleged Vendetta
Alan, says Alison, had “turned into this person with no hobbies and no interests and no life of his own.” Alison also says he was a heavy drinker prone to aggression when intoxicated, but he had been sober for about seven years until Jennifer announced she was ending things.
Alison says that when her mom decided to leave him Alan “was like, ‘I don’t know how she can do this to me,’ very much taking the victim kind of stance. He was pretty delusional about the whole situation.”
After the slayings, Alison told police about alleged “incidents of domestic violence” that were never reported, according to the search warrant affidavit.
Alison tells PEOPLE the deaths of her mother and grandmother have made her even more aware of the complicated burden faced by women in abusive relationships. She urges others to be vigilant and take steps to protect themselves.
“That’s my biggest takeaway,” she says, “and my biggest message.”
Fashion Deals Update: