More than two years after two teenage girls were murdered after going for a walk, Indiana State Police revealed a new photo of the suspect in the slayings Monday while making an impassioned plea to the killer, who's still on the loose.

ISP Superintendent Doug Carter said the investigation into the 2017 killings of Libby German, 14, and Abby Williams, 13, has now shifted to focus on someone who lives in Delphi, Indiana or used to live in the city located about 60 miles northwest of Indianapolis.

"We believe you are hiding in plain sight," an emotional Carter said at a news conference in a plea to the killer. "For more than two years you never thought we would shift to a different investigative strategy, but we have."

2017 DELPHI MURDERS OF 2 TEENAGE GIRLS MOVING IN 'NEW DIRECTION,' INDIANA STATE POLICE SAY

Carter released a new sketch of a suspect that appears to be much younger than the previous sketch released by police. The suspect now is believed to be a man who is between the ages of 18 and 40, but might also appear younger. The man is also believed to have lived, worked, or regularly visited Delphi.

Authorities were able to create the sketch that "more accurately" depicts the face of the suspect from the video recorded on German's cell phone while she and Abigail were on the High Bridge.

"We have a witness. You made mistakes," Carter said. "We are coming for you and there's no place for a heartless coward like you to hide that gets his thrill from killing little girls."

Besides the sketch, Carter also revealed that investigators were looking for the owner of a vehicle abandoned on the east side of County Road 300 North next to the Hoosier Heartland Highway between 12 p.m. and 5 p.m on Feb. 14, 2017. The vehicle was parked at the old CPS/DCS/Welfare building, according to Carter.

The teens were reported missing on Feb. 13, 2017, after they were dropped off at the Delphi Historic Trails in the early afternoon. Their bodies were discovered the next day by a volunteer, about a half-mile off the trail.

Despite autopsies being conducted, no cause of death has ever been revealed for either of the girls. Police have tens of thousands of tips in the investigation into Williams' and German’s deaths but have not yet made any arrests.

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"We likely have interviewed you or someone close to you," Carter said in a message to the killer. "We know that this is about power for you, and you want to know what we know. One day, you will."

In the course of the investigation, authorities released a pixelated image of a man walking on the bridge around the time of the girl's disappearance. A new brief video of the man walking was released on Monday in the hopes that someone could identify the man based on the mannerisms as he walks.

Authorities also released an audio clip from one of the girl's phones. Police said it might be the suspect’s voice. An unidentified man can be heard saying: “Down the hill.”

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Carter said the girls' families learned about the latest developments Monday morning and asked the media to give the family two weeks before commenting on the new information, according to FOX59.

In the years since the teenager girls were killed, authorities had probed a possible connection between the murders and a man accused of child molestation, after the public drew similarities between his mugshot and an FBI sketch of the alleged killer.

Delphi investigators had also worked closely with detectives in Fort Wayne, Indiana. after John. D Miller was arrested last year in the 1988 murder of an 8-year-old girl. Authorities, however, would not comment at the time if he was a possible suspect in the two teenagers’ deaths.

Authorities are encouraging anyone with information to contact the tip line at 844-459-5786 or email them to Abbyandlibbytip@cacoshrf.com.

Fox News' Katherine Lam and Paulina Dedaj contributed to this report.