Mystery deepens in double murder of Delphi girls Abby Williams and Libby German

The mysterious murder of two Delphi girls deepened this week when Indiana State Police revealed new clues about the killer, including that he may live in the tight-knit Indiana community.

But this new information -- including a new sketch and more video evidence -- seems to leave the public with more questions than answers.

The crime

Eighth-graders Abby Williams, 13, and Libby German, 14, were enjoying a day off from school on Feb. 13, 2017, when they vanished on a hiking path.

Their bodies were found the next day near the trail.

A new sketch

The male suspect -- seen in this new sketch released on Monday -- is believed to be between 18 and 40 years old, but may appear younger than his age, police said.

Police had previously released a different composite sketch of the suspect.

Former FBI agent and ABC News contributor Brad Garrett said the new sketch likely came from a new witness -- "someone that's come forward, maybe alleging to have actually seen the guy they're looking for."

"The difficulty in any sort of sketch is that it's difficult obviously for people to remember exactly what somebody else looks like ... it's not uncommon for sketches to not necessarily look like the person you're looking for," Garrett said, which can translate into false leads.

Callahan Walsh, a child advocate with the National Center for Missing and Exploited Children, agreed.

"I think they have some new information. I think they have a new eyewitness who has come forward," he told "Good Morning America" Tuesday. "The [new] sketch isn't created from the video. A sketch like that is mostly done when someone is describing what a person looks like -- it's not a computer generated image from that video."

Over 1,000 tips have been submitted since Monday's news conference, authorities said on Tuesday. Authorities said tips on the suspect sketch is their main focus.

'Hiding in plain sight'

The killer is believed to currently or previously live in Delphi, work in town or visit on a regular basis, Indiana State Police Superintendent Douglas Carter announced Monday.

"We believe you are hiding in plain sight" and even "may be in this room," Carter said at a news conference.

"We likely have interviewed you or someone close to you," Carter said.

From the beginning, Garrett said he believed the killer was local and "attached to this community" of nearly 3,000 people.

"Carroll County, Indiana, is very rural ... when the superintendent of the police says 'local,' that's not just the town of Delphi. That's Carroll County," Garrett said. "This person could well live 15 miles from Delphi, but they're from here, they know that trail, they walk that trail ... it's reasonable to think that the killer isn't down the street from the trail, but he's in the proximity."

Garrett said that particular trail likely wouldn't have visitors from outside the area.

"The idea that a random person would happen to be walking down the railroad track and happen upon these two victims, and that they had never been there before, I think is low," Garrett said.

Serial offenders often do not leave the area where they committed their crimes, Garrett said, because "they feel comfortable that they're not gonna get caught."

"This particular killer, he's on a remote trail -- if he believes that nobody else saw him actually harm these two girls, then in his mind, he feels like he's home free," Garrett said.

"He's going to be somebody that is pretty good at keeping his mouth shut. That doesn't mean somebody doesn't know something, but he's been very good at maintaining his lifestyle," Garrett continued. "Some killers have an innate ability to do that ... it goes with criminals' ability to place their life in boxes -- commit these crimes, do awful things, continue on their normal life."

Walsh said it's likely the killer is "very close to the investigation" and is likely "trying to take the temperature of the investigators to determine what they know and how hot on his trail they are."

"It's not unlikely he could have been a volunteer in the search" for the girls that first day they went missing, Walsh added.

Abandoned lot

Officials also said a car was left in the parking lot of an abandoned building in Delphi on the afternoon the girls were killed.

Police are now looking for anyone who can provide descriptions of cars in the lot at that time.

The building has since been demolished and the lot is empty, police said.

Carter did not elaborate on the car's involvement in the case. But Garrett said he believes investigators either just learned about the car recently or were unable to find the driver.

"Maybe this car has taken on a different significance in this investigation," he said.

Video and audio clips

In 2017, police released a grainy image of someone seen on the trail the day the girls went missing along with a chilling recording found on Libby's phone with just three words heard: "Down the hill."

On Monday, state police released new audio and video footage from Libby's phone.

The brief video clip shows the suspect walking on the bridge near where the girls were last seen.

"When you see the video, watch the person's mannerisms as they walk," Carter said Monday. "Do you recognize the mannerisms as being someone you might know?"

It's hard to decipher what the suspect says in the new audio clips.

"The person talking ... is the person on the bridge with the girls," Carter told reporters. "Please listen to it very, very carefully."

Garrett said he doesn't understand why state police waited two years to release the additional footage.

"The critical window many times in catching people quickly is to release as much evidence as you can that won't compromise the case -- maximum amount of video, maximum amount of audio that you can get out there to trigger somebody to come forward," Garrett said. "That's how you get really good tips."

But to Walsh, the delayed release of the video and audio helps keep "the community invested in this crime."

"And if anybody out there who did know anything and maybe it's weighing on their conscience, they're seeing it out there again and they're getting a reminder that they need to do the right thing," Walsh said.

Walsh thinks Monday's press conference was an appeal to the community in hopes that more eyewitnesses will come forward.

"People sometimes think their tip may be insignificant so they don't say anything -- but it can often be the key that unlocks the door to justice," he said.