CHICAGO (CBS) — Indiana State Police have released a new sketch of the man suspected of killing 13-year-old Abby Williams and 14-year-old Libby German in Delphi in 2017, along with additional audio and video from Libby’s phone.

The new sketch released Monday is significantly different than one released two years ago.

Indiana State Police released a new sketch of the man suspected of killing two teenage girls, Libby German and Abby Williams, in Delphi in February 2017. (Source: Indiana State Police)

An old sketch of the suspect shows him wearing a hat, and with facial hair, but the new sketch shows him clean shaven, with no hat. The facial features — including the shape of his chin, eyes, and nose — also are much different in the new sketch, but police did not explain the changes.

Sketch of suspect in murders of two Indiana teens. (Credit: FBI)

Indiana State Police Supt. Douglas Carter said he believes the girl’s killer is “hiding in plain sight.” He said police are looking for the driver of a vehicle abandoned on County Road 300 North next to the Hoosier Heartland Highway on the day the girls disappeared. The vehicle was parked at the old Child Protective Services/Department of Child Services/Welfare building in Delphi.

“For more than two years, you never thought we would shift gears to a different investigative strategy, but we have,” he said. “We likely have interviewed you, or someone close to you. We know that this is about power to you, and you want to know what we know. One day you will.”

Carter said investigators believe the killer is 18 to 40 years old; and is either from Delphi, works there, or is a regular visitor.

“He could be in this room,” Carter said at a news conference on the investigation.

Carter also delivered a message to the girls’ killer.

“What will those closest to you think of when they find out that you brutally murdered two little girls? Two children. Only a coward would do such a thing,” he added. “We are confident that you have told someone what you have done, or at the very least they know because of how different you are since the murders.”

Abigail J. “Abby” Williams and Liberty Rose Lynn “Libby” German disappeared while they were hiking on the Monon High Bridge Trail near Delphi in February 2017. Their bodies were found a day later on Valentine’s Day in a wooded area a quarter-mile from an abandoned railroad bridge that’s part of a trail system where the teens had planned to go hiking during a day off from school.

Abigail Williams (left) and Liberty German (right) (Credit: Facebook)

Days after their deaths, police released audio recovered from Libby’s phone, in which a man’s voice is heard saying “down the hill.”

On Monday, police released a slightly longer version of that recording, a man’s voice saying, “Guys … down the hill.”

Police also released a very short video of him walking on a set of abandoned railroad tracks near where the girls were found dead. Investigators had previously released a still frame of that video.

Anyone with information about the should send tips to abbyandlibbytip@cacoshrf.com; or call the FBI tip line at 844-459-5786, or Indiana State Police at 800-382-7537, or Carroll County Sheriff’s Department at 765-564-2413.