Police say one of the two teenage girls killed last week in Delphi, Ind., may have recorded the voice of a suspect just before they died. At a Feb. 22 news conference, police played an audio clip of a man's voice saying "down the hill." The recording came from victim Liberty German's cellphone. (Reuters)

Police have long believed they know the voice of a man suspected of killing two teenage girls hiking near an old railroad bridge outside of Delphi, Ind.

Now, they want the public to see his face.

Indiana State Police investigators have released an artist’s composite sketch of the double-murder suspect, hoping someone in the public can help solve the 4-month-old killings of 14-year-old Liberty German and 13-year-old Abigail Williams.

The pair were reported missing on Feb. 13 by their families, who had dropped them off to let the girls hike the Delphi Historic Trails, according to a news release. Their bodies were found the next day by volunteers who’d organized a search when they didn’t return home.

Investigators have focused their efforts on a man seen walking alone on the trail.

Early in the investigation, police released an eerie recording captured on Liberty’s cellphone using its video camera function — a male voice saying “down the hill” — hoping it would be enough for someone to recognize the person speaking.

It wasn’t. And the double homicide remains open four months later.

Authorities also released a blurry photograph of a man wearing jeans and a blue jacket walking on a path in front of some trees. He has brown hair and appears to be walking with his hands in his pockets.

Indiana State Police Sgt. Kim Riley told Indianapolis Fox-affiliate WXIN that the sketch was a “very important development” that gives people “a better view of the person.”

“It shows a little more facial features it gives you a little more information on what we’re looking at, who the suspect might be, and that’s why we feel that it’s very important that this picture is out there at this time,” he said.

Police believe the man in the sketch is between 5-foot-6 and 5-foot-10 and weighs 180 to 220 pounds. He has reddish brown hair. Police asked the public to pay special attention to his facial features.

“Someone knows who this individual is,” Indiana State Police Superintendent Douglas Carter said at an earlier news conference. “Is it a family member? Is it a neighbor? Is it an acquaintance? Is it an associate? Or maybe that one guy, who lives over at that one place that just kind of not right.”

Read more:

Texas sheriff’s deputy and her husband charged with murder in chokehold at Denny’s

A body cam captured a cop’s violent encounter with a teen — but a new law keeps the video secret

‘I was just reading a book’: Canadian cops called on black man reading C.S. Lewis in his car

Aren’t more white people than black people killed by police? Yes, but no.