Mom hopes composite sketch will help crack unsolved killings of Indiana teens Abby Williams, 13, and Libby German, 14, vanished while hiking on Feb. 13.

 -- Indiana State Police today released a composite sketch of a man believed to be connected to the unsolved killings of eighth-graders Abby Williams and Libby German, and Abby's mother says she hopes this is the "piece of the puzzle" that will lead to an arrest.

Abby, 13, and Libby, 14, who became good friends as teammates on their seventh-grade volleyball team, were enjoying a day off from middle school on Feb. 13 when they disappeared on a hiking trail near their rural hometown of Delphi. Their bodies were found the next day.

In the over five months since their deaths, no arrests have been made.

Until today, police had only released two clues -- the grainy image below of a man who police say is the prime suspect in the investigation and a chilling recording found on Libby's phone with just three audible words: "Down the hill."

Today, the state police released this detailed sketch of who they say is believed to be connected to the slayings, saying the "composite drawing is the result of information received during the course of this ongoing investigation."

Abby's mother, Anna Williams, told ABC News today the new sketch "means we are just one step closer."

"Nothing you do now is going to bring the girls back. But the person who did this is going to have to pay the consequences for that," she said. "We really truly hope that this is the piece of the puzzle that we need to bring justice to our girls."

The person depicted in the sketch is described as a white man with reddish brown hair, standing between 5 feet, 6 inches, and 5 feet, 10 inches, and weighing 180 to 220 pounds. The hat in the sketch may not be accurate, police said, adding that the public is asked to focus on the person’s facial features.

A reward over $230,000 is available for information leading to an arrest. Anyone with information about the case or the person depicted in the sketch is asked to contact the tip line at 844-459-5786 or abbyandlibbytip@cacoshrf.com.

"Keep sharing the picture, keep sharing the tip line. Anything and everything helps," Williams said. "We now have a better sketch, and now we just need a name.”

In May, three months into the investigation, Libby's grandmother told ABC News she was confident the girls' killer would be caught eventually.

"I have faith," Libby's grandmother, Becky Patty, said. "I have faith and I'm thankful to law enforcement, to the media, to all the private individuals helping. Between everybody, I'm confident we can catch him."

Police said today the case is still very active and they are receiving about five to 10 tips a day.

ABC News' Alex Perez and Andy Fies contributed to this report.