The mysterious murder case of a Canadian girl was solved after police found clue in the Facebook selfie posted by her friend. Brittney Gargol, 18, was found dead near a landfill in March 2015 and an autopsy later revealed that she died of strangulation.

On Monday, Gargol's friend Cheyenne Rose Antoine, 21, pleaded guilty to manslaughter in Saskatoon Provincial Court in connection with the death. Police arrested Antoine after they found a Facebook selfie that showed her wearing the belt used to strangle her friend.

The wide blue woven belt with a large buckle was found on a roadside next to Gargol’s body, and Antoine was seen wearing the same belt in a photo posted to her Facebook account just hours before the killing, according to the Saskatoon Star Phoenix.

“Where are you? Haven’t heard from you. Hope you made it home safe,” Antoine had posted on her victim's Facebook wall after the killing.

Investigators got suspicious of her when she initially told them about spending time with the victim the night she died, but left her friend to visit her uncle. It was later revealed that her statement was false. Antoine later told investigators that she and Gargol partied with two men, who allegedly strangled the victim and put a gun to her head to help them. The second statement was also proved false.

Investigators arrested Antoine last year after finding the selfie showing her wearing the same belt used to kill her friend.

“It’s quite remarkable how the police developed this information,” prosecutor Robin Ritter said Monday in court, adding that Antoine poses a threat to public safety.

She “has issues … and because of those issues, she is dangerous,” the CBC reported.

Crime Tape A representational image of a crime scene. Photo: Getty Images/ Christopher Furlong

While describing how the events unfolded leading up to Gargol's death, Antoine said that she and the teenager were best friends and were out drinking when they got into an argument. Antoine did not deny killing Gargol but said she had no memory of strangling her friend. 

“I will never forgive myself,” she said in a statement read in court.

Gargol’s father, Everett Hillbom, said in a statement that he was angry and sad that Gargol’s life was cut short. 

“You were her friend. She trusted you,” Gargol’s stepmother, Kristi Wickenhauser, told Antoine, adding that she could have taken Gargol to a hospital instead of leaving her to die in the street. 

Describing how Gargol's death affected the family, the victim's aunt Jennifer told the court, "Most days we can't stop thinking about Brittney, what happened that night, what she must have felt fighting for her life." She added, "You feel darkened in your own dark world … You robbed this world of someone who had a special gift."

At her court appearance Monday, Antoine’s lawyer, Lisa Watson, said her client suffered through sexual, emotional and physical abuse as she grew up in foster care, CTV reported. 

“My client had some very deep-seeded personal issues that she was not dealing with and unfortunately, for whatever reason, we’ll never know, they turned into a very tragic situation for all involved,” Watson said.