VIDEO: Face and voice of a killer: Teen girls captured the man police are hunting for their double murder on camera saying 'down the hill' Liberty German, 14, and Abigail Williams, 13, were found murdered on February 14 near a scenic hiking trail outside Delphi, Indiana Police revealed Wednesday that Liberty captured the prime suspect in the twin murders on her phone He was recorded saying 'down the hill' in an audio clip released by troopers hunting for the suspect The two girls were last known to be alive on the same bridge where Liberty photographed and recorded the man This is the prime suspect in the murders of Indiana teenagers Abigail Williams and Liberty German, police said Wednesday - recorded by Liberty before her death.Authorities had released the picture last week saying they were looking to speak to the man but stopped short of calling him a suspect.Police said on Wednesday that Liberty, 14, had taken the picture of the man on her cell phone.Revelation: Indiana State Police Superintendent Doug Carter said the voice of the killer was a key clue which he hopes someone would recognize. Libby posted these Snapchat photos of Abigail at Monon High Bridge Trail close to when they started hiking around 2.07pm Monday 13 February. They are the last photos of the girl. Both were founded murdered three-quarters of a mile away the next day An audio file from German's cell phone was also released with police saying that she had 'the presence of mind' to turn her video camera on.The tape consisted of three words: 'Down the hill'. Police asked for the public's help in identifying the voice.On Wednesday morning, police appealed to the public to come forward with any information on the man who was seen on the abandoned train tracks on the Delphi Historic Trails at the same time on February 13 when Williams, 13, and German, 14, went missing on a hike.FThe two friends were active on social media on their phones before they disappeared, with German posting final Snapchat images of Williams walking on the bridge, which is 60 feet above the creek, at 2:07pm.In the grainy image, the man, can be seen walking with his head down and hands in his pockets. He is dressed in jeans, blue jacket and a hat.Indiana State Police Sgt. Tony Slocum said: 'We are actively looking for this person. This person is our suspect.'