US police investigating the killing of two teenage girls have released evidence they hope will lead to the killer's arrest.
Media reports state that the evidence was found in a video clip which was retrieved from the phone of one of the victims.
The bodies of the two girls, Liberty Rose Lynn German (14) and Abigail Jay Williams (13), were found on Tuesday after they failed to return from a hike.
Organised searches led to the discovery of their bodies which were found outside Delphi in a wood near Deer Creek, around three-quarters of a mile from where they had been dropped off to go hiking.
The words "down the hill" can be heard on the audio recording and police have said that it's enough to recognise the person's voice. Investigators said they believe the clip was recorded as a crime was about to occur.
The rest of the video and other evidence from the girl's phone will not be released because of the ongoing investigation.
"Someone knows who this individual is," Indiana State Police Superintendent Douglas Carter said. "And if you're watching, we'll find you."
Authorities and community leaders are offering a $41,000 reward for any information leading to an arrest.