In a major breakthrough Monday, Indiana State Police announced the arrest of Richard Allen for the 2017 double slaying of teens Liberty "Libby" German and her best friend, Abigail "Abby" Williams.

Allen, 50, who worked as a pharmacy technician at CVS in Delphi, a town of about 3,000 people, has been charged with two counts of murder.

"We haven't closed the door on the investigation," Carroll County Prosecutor Nicholas McLeland said when asked if other suspects were being probed. "We're not presuming anything at this point."

Officials did not disclose key details, including how the girls were killed or the evidence they've obtained so far. Here's a timeline of the case.

DELPHI MURDERS: SUSPECT ARRESTED FOR THE 2017 SLAYINGS OF TWO TEENS

Richard Allen booking photo

Authorities announced Monday the arrest of Richard Allen, center, for the murders of Libby German, left, and her best friend, Abby Williams, in Feb. 2017. (Indiana State Police)

Feb. 13, 2017 

German's sister dropped off the girls at the entrance to the Delphi hiking trail near the Monon High Bridge at 1 p.m during a day off from school.  

The teens didn't show up at a predetermined meeting spot and their families reported them missing at 5:30 p.m., according to police.

Feb. 14, 2017

A search team found German, 14, and Williams, 13, dead in a wooded area half a mile from the Monon High Bridge, which is about 70 miles northwest of Indianapolis. 

Feb. 15-25, 2017

Investigators released a pair of grainy photos of a suspect walking on the abandoned railroad bridge and an audio recording of the man ordering the girls "down the hill." 

DELPHI MURDERS: INDIANA MAN REPORTEDLY IN CUSTODY IN CONNECTION WITH 2017 KILLINGS OF 2 GIRLS

The images and recording came from German's cellphone, officials said.

Suspect composites in Delphi case

A composite sketch of the suspect from 2019, left, and the earlier sketch from 2017, far right. A photo police recovered from German's cell phone of the man walking toward them on the railroad bridge (middle). (Indiana State Police)

State Police and the FBI executed a series of search warrants in connection to social media accounts under the name "anthony_shots." 

The fictitious account was used by Kegan Kline, 27, to communicate with young girls, including German. It was later revealed that Kline had chatted with German the night before she vanished.

March 17, 2017

Authorities executed a search warrant on Ron Logan's property, where the teens were found. He is not a suspect in the murder, according to FOX 59.

July 17, 2017

Five months after the killings, police released a sketch of the suspect based on witness tips. 

Kegan Anthony Kline mugshot

Kegan Kline's booking photo in child pornography case. (Miami County Sheriff's Office)

April 22, 2019 

An updated sketch depicted a much younger male suspect. State police announced that the case had "shifted in a new direction" and described the suspect as between the ages of 18 and 40. 

WATCH THE DELPHI MURDERS ON FOX NATION

Police also released for the first time video of the suspect walking on the railroad bridge recovered from German's phone.

Kegan Kline linked to 'anthony_shots' Instagram

In December 2021, the Indiana State Police said in a Facebook post that they had uncovered a fictitious Instagram account under the username "Anthony_Shots" in their investigation into the Delphi murders.  (Indiana State Police)

August 19, 2020

Kline is charged with 30 felonies stemming from alleged possession of child porn.

April 27, 2021

The Carroll County Sheriff's Office says it is probing James Brian Chadwell after he was charged with an attack on a 9-year-old girl.

March 25, 2022

A transcript of a 2020 police interview with Kline is obtained by the podcast "Murder Sheet." 

Kline allegedly admitted to communicating with German, and police say he had planned to meet her at the bridge the day she was murdered, which he denied.

 The transcript also revealed that he had searched "How long does DNA last" on his computer and failed a polygraph test.

Feb 13, 2022 

 Kelsi German told WTHR on the anniversary of the murders that she still believes her slain sister, Libby German, will get justice.  

"When I’m feeling frustrated, when I feel like no answers are coming and I’m feeling dejected, I say that. I say, ‘Today is the day. It’s coming and it’ll get here. We’re going to have answers’ and just reaffirm myself and say, ‘It’s hard, it’s frustrating, it’s been five years, but we’re going to have answers eventually. It’s coming.'" 

Oct. 31, 2022 

Kelsi German's prayers were answered when state police announced the arrest of Allen at a press conference Monday. 

Indiana State Police Superintendent Doug Carter speaks at press conference Monday

Indiana State Police Superintendent Doug Carter announces during a news conference in Delphi, Indiana, Oct. 31, 2022, the arrest of Richard Allen, 50, for the murders of two teenage girls killed during a 2017 hiking trip. (AP Photo/Michael Conroy)

"We got him," she wrote on Twitter. Police said the investigation is still ongoing and did not say whether Kline remains a suspect. 

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If you have information on the Delphi murders, please contact authorities at abbyandlibbytip@cacoshrf.com or call 844-459-5786, 800-382-7537 or 765-564-2413.

The Associated Press contributed to this report.