For Helen Hargan, 2017 was a year of new beginnings.
Excited about the future, the bright Southern Methodist University grad was gearing up for her next chapter when she moved back home to the Washington, D.C. suburb of McLean, Virginia, that spring while she waited for construction on a new house to be finished.
She moved in to the $1.3 million colonial with her mother, Pamela Hargan, 63, a successful human resources executive, joining her oldest sister, Megan, and Megan’s 7-year-old daughter, who’d both been living there for several years.
There was no room at the house for her three beloved dogs, Helen said at the time, so she made the difficult decision to board them.
“Helen was completely torn up when she dropped the dogs off,” Tamara Belotti, of Dancing Creek Farm in Cascade, Virginia, tells PEOPLE.
“Those dogs were everything to her. Her goal was to do what she had to do, create a home and get her dogs back.”
That would never happen.
On July 14, 2017, Fairfax County Police responded to a 911 call about a possible shooting at the Hargan home and found Helen and her mother dead of apparent gunshot wounds.
Pamela’s body was found in the laundry room while Helen’s was found in an upstairs bathroom with the muzzle of a rifle laying on her abdomen.
Police at the time said Helen killed her mother before turning the gun on herself — which Pamela’s sister, Tamara North, said she had a hard time believing.
“It didn’t make sense,” she says.
Helen was dating a man her family thought she would one day marry.
“She was beautiful and smart,” says North. “She had everything to live for.”
Want to keep up with the latest crime coverage? Sign up for PEOPLE’s free True Crime newsletter for breaking crime news, ongoing trial coverage and details of intriguing unsolved cases.
North was right, according to authorities. More than a year later, on Nov. 9, 2018, Fairfax County police announced they’d arrested Megan.
Charged with two counts of first-degree murder, Megan had staged the scene to look like a murder-suicide, Fairfax County Police Major Ed O’Carroll said at a press conference.
Megan remains behind bars while she awaits trial, scheduled to begin in June 2020.
She has not yet entered a plea. If convicted, she faces life in prison.
• For more on the tragic murders of a mother, daughter and another daughter accused of killing them, subscribe now to PEOPLE or pick up this week’s issue, on newsstands Friday.
Her lawyer did not respond to PEOPLE’s requests for comment, but said in court records that Megan was not home at the time of the murders.
In an unsealed search warrant obtained by PEOPLE, authorities allege that on the day before the murders, Megan had tried to transfer a large sum of money from her mother’s bank account. Her mother notified the bank.
The next afternoon, Megan allegedly stormed into the laundry room with a rifle and shot her mother in the head.
Helen hid in a nearby bathroom, sobbing hysterically into the phone to her boyfriend in Texas, frantically telling him her sister was “downstairs transferring money” after shooting her mother, court documents show.
Minutes later, Megan allegedly headed back upstairs and shot her sister in the head.
“I was absolutely horrified that Megan would do this,” says North.
With investigators labeling the death a murder-suicide for more than a year, Helen took the blame for the tragedy. “Helen didn’t deserve that,” says North.
Belotti is still caring for Helen’s “sweet” dogs — one of them a deaf senior — mostly at her own cost, because she hasn’t been able to find homes for them yet. (She is looking for interested adopters.)
“She was clearly a responsible, loving owner,” she says. “She checked in on them often. When I found out she had died, I felt such sadness.”