Antoine, now 21, was initially charged with second-degree murder, but pleaded guilty to a lesser charge of manslaughter in a Saskatoon courtroom on 15 January 2018.
The Facebook photo showed Antoine wearing a belt identical to the one that was found near Gargol's body.
It seemed like the death of the girl was an unsolvable case, but then police chose to dig up some information on Facebook and that is when they saw the murder weapon in a photograph.
Antoine ending up drunkenly confessing to the murder to a friend, claiming that the two girls were drunk and high when they got into a fight. She was found strangled to death near a landfill with a belt near her body. Haven't heard from you. "Hope you made it home safe", Antoine wrote. A series of tips later led police to a witness who said Antoine had admitted arguing with Gargol and choking her.
Police spoke with Antoine about Gargol's death, but she gave false evidence to police to throw them off the trail.
But her story began to fall apart when police checked CCTV and found the women hadn't visited one of the places as she had claimed.
It was the same belt Antoine was seen wearing in that photograph on the last night of her friend's life.
It was reported that Antoine had gone to another friend the same night in which the murder happened in a hysterical state.
"It's quite remarkable how the police developed this information", prosecutor Robin Ritter told CBC.
According to the newspaper, Antoine had reportedly posted on her friend's wall saying, "Where are you?" Afterward, Antoine said she went to her uncle's. "Say hello to my mommy up there for me!"
Gargol's family provided victim impact statements during Antoine's sentencing.
"You were her friend. She loved you, she respected you and she trusted you", Wickenhauser said. I am very, very sorry...
In comments reported by CTV News, she said: "I'll never forgive myself. It shouldn't have ever happened", she said in an announcement through her legal advisor.