Two teenagers disappeared while hiking in 2017. Last week, a man was charged with murder

CNN  — 

As investigators announced Monday that a suspect has been arrested in the 2017 killing of two teen girls in Delphi, Indiana, they also implored the public for any information they may have and said the investigation “is far from complete.”

Richard M. Allen, 50, was arrested Wednesday and charged with two counts of murder Friday in the deaths of Abigail Williams, 13, and Liberty German, 14, officials said. He pleaded not guilty, prosecutors said.

The teenagers disappeared on February 13, 2017, while hiking along the Delphi Historic Trails, about 75 miles northwest of Indianapolis. They were reported missing after not showing up to a meet-up location agreed upon with family. An extensive search revealed their bodies the following day along a railroad bridge near Deer Creek.

Years after the killings, investigators are still grappling with many unanswered questions in the case.

“This investigation is far from complete,” Indiana State Police Superintendent Doug Carter said Monday during a news conference.

“We are going to continue a very methodical and committed approach to ensure that if any other person had any involvement in these murders in any way, that person or persons will be held accountable,” Carter noted.

Tip lines remain open, Carroll County Prosecutor Nick McLeland said Monday, noting investigators are seeking information “not only about Richard Allen, but about any other person you may have.”

McLeland declined to elaborate on whether authorities are seeking additional suspects.

As the investigation continues, here’s what we know so far:

Allen lived in Delphi with his wife and cat, a couple who lives near the suspect said.

The couple, who asked not to be named, said there were rarely visitors at Allen’s home. They frequently saw him in his driveway smoking cigarettes and drinking beer after work, they said.

At the time of his arrest, Allen was working for CVS, the company confirmed in a written statement.

“We are shocked and saddened to learn that one of our store employees was arrested as a suspect in these crimes. We stand ready to cooperate with the police investigation in any way we can,” the CVS statement said.

Officials have not said how they determined Allen is a suspect in the case.

McLeland said a judge concluded there was probable cause to charge Allen with murder, but the prosecutor declined to elaborate on the reasoning.

The charging documents and probable cause affidavit were sealed, McLeland noted. A court will review the decision to seal the documents, he said.

Allen has a pretrial hearing slated for January 13 and his trial is scheduled for March 20, McLeland added.

Carter told HLN after the announcement of Allen’s arrest Monday that state police were already receiving new tips, but he declined to elaborate.

“There’s no one on the planet that would love to tell this story more than me right now, but I can’t,” he said, noting doing so could jeopardize the criminal case.

The couple who live near Allen described spotting unmarked police vehicles at his home last month.

The couple said they saw a deputy arrive at Allen’s home on the night of October 13 with a sheet of paper. After the deputy showed Allen the paper, police began searching the house and yard, the couple said.

As Allen remained outside, officers left the house with bundles of cloth or clothing, a stack of books, a shopping bag and a shoebox, the neighbors said. A tow truck drove away with Allen’s black SUV, they said.

One of the neighbors asked a deputy whether he should be worried, to which the deputy replied, “Just remain vigilant, especially with your wife and daughters.”

Before the girls were killed, Liberty captured an image of a man dressed in a blue jacket and jeans on the bridge near where their bodies were found. Indiana State Police investigators released the image, saying they believed the man was a suspect in the double homicide.

Later, state police released audio of the alleged killer saying, “… guys … down the hill” – in hopes the public might identify the suspect’s voice.

Liberty’s grandparents – Mike and Becky Patty – referenced the evidence in an interview with HLN about Allen’s arrest, saying, “There’s a face to the bridge guy now. And a name with the bridge guy.”

“If there’s anything out there that law enforcement doesn’t know about, we want them to know about it. And especially with this arrest, and this person being charged with this,” Mike Patty said.

In the meantime, the family is still trying to wrap their heads around the arrest, which came five-and-a-half years after the killings.

“I think the reality of it is still setting in,” Mike Patty said. “And more importantly, trying to figure out what our path forward is, and that is the prosecution of the case.”

“You feel it, you live it every day,” Becky Patty added. “She may not be here physically, but we take her with us everywhere we go.”

Liberty’s aunt, Tara German, said she’s a regular at the CVS where Allen worked and she knew him from shopping at the store.

She recounted an exchange she had with him while she was printing photos for her niece’s funeral.

“I went into the store to print photos of Libby for the funeral, and he was the one who helped me,” German said. “I was a mess trying to get the images off my phone. Once they were printed, he looked at me and said, ‘I’m not gonna charge you for this.’”