The 2015 murder of an 18-year-old girl ended in a conviction earlier this month, thanks to a Facebook selfie.

Two years ago, the body of 18-year-old Brittney Gargol was discovered on a road near the Canadian city of Saskatoon in Saskatchewan. Years went by before police arrested Gargol’s best friend, Cheyenne Rose Antoine, for the murder.

Police described a “long and complicated investigation” that was cracked open in part by a selfie on Facebook. In the selfie, posted six hours before the body was found, Antoine is seen wearing a belt that matched one found near Gargol’s body. An autopsy determined that Gargol died of strangulation, and it was believed the belt was the murder weapon.

Police used more Facebook posts to determine the timeline of the events leading up to and following Gargol’s death. Antoine attempted to hide her involvement with posts in the hours after Gargol’s death. “Where are you? Haven’t heard from you. Hope you made it home safe,” Antoine posted to the victim’s page.

“It’s quite remarkable how the police developed this information,” said prosecutor Robin Ritter.

Antoine had initially told police that she and the victim went to several bars together, and then Gargol left without her. After investigating security tapes of one of the bars, police determined that the two girls were never there. A tip eventually led police to an unnamed witness, who said that Antoine had confessed to killing the victim.

Police eventually determined that Antoine had been drinking and doing drugs on the evening of the murder. She and Gargol got into a fight, and she hit and then strangled her friend.

Antoine was charged with second-degree murder. She pleaded guilty in January, on the day preliminary hearings were scheduled to begin, and was sentenced to seven years in prison.

“Honor your friend by becoming a positive member of the community,” Judge Marilyn Gray, who sentenced Antoine, admonished her. “You owe it to her.”

Antoine claims she does not remember killing her best friend, but accepts responsibility for the murder. “She knows the family would like an explanation, a reason, but unfortunately she can’t provide that,” said Lisa Watson, Antoine’s attorney.

In a statement read to the court through her attorney, Antoine said “I will never forgive myself. Nothing I say or do will ever bring her back. I am very, very sorry. . . .  It shouldn’t have ever happened.”

Antoine suffered years of abuse at the hands of her foster parents, and had turned to drugs and alcohol. “My client had some very deep personal issues that she was not dealing with, and unfortunately they turned into a very tragic situation for all involved,” said Watson.

Members of Gargol’s family also made statements. “Most days we can’t stop thinking about Brittney, what happened that night, what she must have felt like fighting for her life,” said her aunt, Jennifer Gargol.

Al Gargol, the victim’s uncle, said outside the courtroom that she was “a wonderful young person that didn’t deserve this and we truly miss her every day.”