Eerie photographs show the hill two young teens were ordered to walk down by their killer before he murdered them in rural Indiana.
This is the location of the final death march by Abby Williams, 13, and Liberty German, 14, after they recorded their murderer's chilling command to go "down the hill".
The murder investigation's chief detective, who has heard the entire tape from which the audio fragment comes, describes the killer as having the "voice of the devil" coming through him.
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Libby German recorded the killer's order after she placed her phone with its video camera rolling in her pocket as he cornered them on the bridge.
Indiana local LH, who didn't want to be identified, told news.com.au that she finds the spot the girls met and filmed their murderer so creepy, she takes a gun whenever she visits.
LH, who has visited the location multiple times, describes in detail the spot where the schoolgirls were abducted on February 13, 2017.
It is the Monon High Bridge, a hiking trail near the tiny Indiana town of Delphi, 100km northwest of Indianapolis.
"When you are walking down the trail and approaching the bridge, the trail makes a turn and you can slowly see it 'approaching' you," LH said.
"This felt so very creepy to me.
"I don't know if that's just me or what but that bridge and walking up to that bridge around the curve feel evil."
LH revealed the bridge is higher and more treacherous than it looks, and some of the cross posts – called "ties" - are missing or rotten.
The hill the girls were forced down is steeper, and once on it, a person would feel "trapped with no way out".
"The girls should have not been on that bridge," LH said.
"One thing we know about that killer … it's pretty obvious that the guy wasn't scared of heights.
"Nobody actually said it [but] he must not be to walk on a bridge like that … or he walked that bridge many times."
The teens were found dead "down the hill" the following day. Their bodies bore "strange … signatures" at the kill site across Deer Creek in woodland 2km out of town.
"The bridge is a lot bigger than it looks in photos," said LH, whose fear of heights meant, initially she "crawled across" the 7.5 storey-high structure.
"It is maybe ten feet [3m] across. The space between the gaps is not enough for your foot to slide through, unless you turn it sideways.
"My foot fell through several times and part of the board went down to the creek.
"Down where you see him on that photo [the image captured by Libby German on her phone] is especially mushy and I was scared there. That's not too far from the end."
A video taken by a local grandfather of the walk along the Monon High Bridge, recorded four months before the murders, shows just how precarious it is to walk on the structure.
The murdered girls, who attended Delphi Community Middle School where they played saxophone and volleyball together, had visited the bridge before the day they died.
The Monon High Bridge trail attracts hunters, fishers, campers and kids hiking or just taking photos of the popular spot.
It was an unseasonably warm day and the best friends were dropped off at 1.35pm for their walk, which started at a location which, LH told news.com.au, has since been fenced off with bent red metal gate.
At 2.09pm, Libby, used her mobile phone to upload a picture of Abby walking on the iconic bridge to Snapchat.
The girls were due to be collected by Libby's grandfather Mike Patty, her legal guardian, in the trail car park at 3.15pm, but failed to show up.
By 5pm, the girls' families were out searching for them and by 6pm most the town, which has a population of about 3000, had joined police, but the girls were not found.
The search resumed the next day and around noon, a searcher spotted the girls' bodies about 15m from the north bank of Deer Creek, on the 12-hectare property of 77-year-old Ron Logan, who was not considered a suspect.
One investigator into the as-yet unsolved murders, has revealed the girls' killer left several "strange … signatures" at the kill site.
It has not been revealed if these odd signatures were part of the murder method or done post mortem.
LH told news.com.au the condition of the bridge had seriously deteriorated in the past three and a half years since the murders.
"Every time I go there … it gets worse and worse, she said, "You can grab onto pieces of wood and pull it right off the ties.
"The place where Libby was standing when she took the video has filled in slightly with brush.
"If they were standing there now, there would have been foliage covering her view of the killer.
"There is moss growing on some spots where the ties are spongy, likely contributing to the decay. There are vines growing on another area.
"[When] … I walked to the bridge, everything is so quiet and calm that it's almost as if that bridge is saying 'I dare you,' while trying to hide the fact that the girls died there.
"People said that there was a guy behind the tree in the photo of Abby in the woods. It is totally impossible to stand in that area, so we know that's not right.
"They … also said there is a guy coming into the bridge which you can see in the picture at the end.
"That isn't a guy, that's a barricade that has been removed and now is standing along the woods."
Speculation has also arisen that the comments by Indiana State Police Superintendent Doug Carter, who is in charge of the case, about the killer's "voice of the devil" comment had hidden meaning.
It has been suggested this meant the crime scene had signs of satanic ritual, but there is no evidence of that nor any indication by police how the girls were murdered.
The body site was about 800m from the high bridge where Libby had photographed Abby the afternoon before.
How the girls were murdered has still not been released, as Carter says, "because only the killer knows".
On Libby's person, police found her mobile phone and on that they found video of a man on the Monon High Bridge.
He is a white male with his hands in his pockets while walking. He is wearing jeans, a navy blue jacket and possibly a cap.
He is walking at a fast pace across the rail bridge planks, which is no mean feat as they are separated by sizeable gaps, towards the girls.
"It's amazing we have a video, we have a still photograph, we have sound and we don't know who this person is," he said.
The video and audio, incredibly captured by Libby as the girls were ambushed and then murdered, has been broadcast around the world and sparked thousands of tips, but led to no arrests.
Both Carter, the local sheriff, other law enforcement and Delphi citizens themselves are convinced because of the location of the girls' abduction and murder, the killer was a local or former resident with intimate knowledge of the site.
One former investigator on the case told podcast Down The Hill (DTH) that the killer – who police have now confirmed they believe is the man Libby captured on her phone – left "a lot of evidence" at the crime scene.
He said someone knows who the killer is but was keeping quiet because of "extreme fear".
"Please, please, come forward and let us know what you know," Carter said.
"There is obviously someone withholding information," Carroll County Sheriff Tobe Leazenby told the conference.
"It could very well be somewhere along the lines someone was even threatened not to reveal the identity of the killer."
Police released two very different sketches of the face of the killer, one soon after the murder and another based on an interview with a person who may have seen the culprit near Monon High Bridge on the day of the murder.
In the second sketch, the man is much younger and with a full head of hair rather than a cap on his head.
Carter said the killer's age had been estimated between 18 and 40.
Both Carter and the sheriff believe the killer has a connection to Delphi, "whether it's an individual that previously lived in our community and knows the area where the girls were located very well, or possibly is still in our community".
"Unless someone absolutely somehow studied that [trail] in great depth, they would not know specifically where certain things were," Leazenby said.
Another theory was the killer worked at the nearby meatworks, which was why he was so rugged up – wearing a hoodie under his blue jacket – on such a warm day.
The DTH podcast theorises that one person with considerable knowledge of the area committed the crime and had been planning it for some time.
DTH said the killer likely grew up walking those woods, or spends a lot of time outdoors and had come to see the bridge as the perfect trap.
After anyone visiting the bridge crosses the creek, the rest of the bridge is obscured on all sides by woodland, creating privacy for anyone committing a crime.
And once you are there you can only go forward to the point where the bridge ends and private property begins.
DTH speculates the man rehearsed his plan, walked the route and was ready to act whenever suitable victims appeared.
He passed the girls on the bridge, then turned back and when the girls noticed him walking back in their direction, Libby started recording.
Gaining control of them with a knife or gun, he forced them to turn northward – and down the hill.
They walked through the wood and across the creek until they reached the spot where they were found and likely murdered there.
Carter said the Monon High Bridge is now considered by some in Delphi as "hallowed ground".
LH told news.com.au the it took her an hour to cross Monon High Bridge and once she had done so, she wasn't going to cross back the same way, crawling on her knees.
"So I went off down at that end, only I went on the other side of the bridge," she said.
"The hill was still pretty steep and my shoes were sliding down in the mud.
"We have a lot of clay here in Indiana so it's like standing on churned butter.
"I didn't want to go on the side where the girls went, because there was a no trespassing sign right by the driveway, and this side looked steeper than the side I went down.
"It was very hard to get through the grass and the terrain to get back.
"Then … I realised I had to cross the creek.
"It was an awful feeling of being trapped with no way out of there. I can only imagine what the girls felt and they had that killer there."