Authorities hunting the killer of two young teens near an old railway bridge in Delphi, Indiana, are investigating chilling similarities to the unsolved double murder of two young cousins in 2012.
Abigail "Abby" Williams, 13, and Liberty "Libby" German, 14, were murdered in the woods after a relative dropped them off to walk the Delphi Historic Trails last month.
The case has sent shockwaves through the Delphi community and left residents terrified - not least because of its eerie parallels with the notorious double murder of two other young girls.
Lyric Cook, 10, and her 8-year-old cousin Elizabeth Collins were murdered hundreds of kilometres away in Indiana but similarities between the cases have proven too compelling for investigators to dismiss as coincidence.
Each set of girls were alone on nature trails when they were kidnapped, murdered and left in the woods on the 13th day of the month.
Lyric and Elizabeth vanished on July 13, 2012 while riding their bicycles on a trail in their hometown of Evansdale, sparking a massive search involving hundreds of police, rescue officers and volunteers.
A pair of hunters came across their remains in woodland at Seven Bridges Park in Bremer County in December that year. Their bodies were too decomposed to determine how they had been killed or whether they had been sexually assaulted.
After hearing about the Delphi murders, Elizabeth's father Drew Collins called detectives working on his daughters' case to make sure it was on their radar. It was.
"I wanted to make sure they were looking at it and they were already 10 steps ahead of me, looking at it. They contacted Indiana State Police," Mr Collins told KWWL.com.
"My heart just breaks for the families. I don't know what they are going through. I know what I went through and our family went through. It is just very hard, It doesn't get easier."
In the case of the Indiana girls, Abby and Libby were last seen alive at about 1pm on February 13 when they were dropped off near Monon High Bridge by a relative who has not been publicly identified but has been cleared by investigators.
At 2.07pm, Libby uploaded at least two photographs to social media platform Snapchat, including one showing Abby walking along the rickety old bridge.
There has been speculation that a person can been seen hiding in the shadows behind a tree in the photographs.
The girls' bodies were found the following day, on Valentine's Day, in a wooded area near Deer Creek, 18m from the water's edge, around a kilometre from where they were originally dropped off.
Indiana State Police later released unsettling images taken from video on Libby's mobile phone of an older man dressed in a hoodie who is believed to have murdered the girls.
In audio recovered, a man's voice can be heard saying "down the hill" but it is not clear whether it belongs to the man on the footage or an unseen accomplice.
Investigators have called Libby a "hero" for having the presence of mind to record the man on video. His image and the voice recording on loop have been released to the public in the hope someone will recognise them but so far nobody has come forward.
The Federal Bureau of Investigation is working with Indiana detectives to build a profile of the killer. Officers have not revealed how Abby and Libby were killed or whether they were sexually assaulted but have confirmed that DNA was taken from the site where their bodies were found.