Indiana teens' double murder reaches 1 month with no arrest

— -- A month after the bodies of two Indiana teen girls were found in the woods, their killer has yet to be caught or even identified.

Carroll County Sheriff Tobe Leazenby told ABC News today he expected to have a suspect in custody by the one-month mark, but he holds out hope that the next tip officials receive will be the one that leads to the girls' killer.

It was Feb. 13 when eighth-graders Abby Williams, 13, and Libby German, 14, disappeared while on a hiking trail near their hometown of Delphi, Indiana. Their bodies were found the next day.

Now, a month later, no arrest has been made, and the only clues that have been released to the public are a photo 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."

Authorities said today they've received 13,000 tips in the teens' case and the reward for information leading to an arrest has grown to $250,000. Leazenby said the latest big spike in tips came after Libby's grandfather, Mike Patty, gave a news conference last Thursday pleading for the public's help.

Leazenby, who said he spoke to Patty on Monday, said, "The tone I hear from his voice ... he still is as much driven and focused as we all are."

"I'm still confident as sheriff in this county that we will resolve this and get justice for Abby and Libby," Leazenby added.

To the killer, Leazenby vowed: "We are going to find you and you will answer to this."

Delphi is a tight-knit community dubbed by the local sheriff as "small-town USA." A network of trails surrounds the town of nearly 3,000 people, and here, everyone knows everyone.

Greg Briles, the superintendent of schools at the Delphi Community School Corporation, told ABC News the students and teachers have "resumed as much normalcy as possible;" however, he added, "we're still very concerned about the individual or individuals who have not been caught ... they're still out there."

Leazenby said there is not necessarily increased security in town, but he said community members appear to be more vigilant.

"People look at people different ways now, I think," Leazenby said. "I think complacency has been at least eliminated at this stage, and it's more of a mindful, watchful, vigilant attitude. I don't want paranoia, and I don't think we've had that, but people literally looking over their shoulder is not necessarily a bad thing in today's society."

At Delphi Community Middle School, where Abby and Libby were eighth-graders looking forward to high school, grieving friends are now painting a "tree of life" on the cafeteria wall with different messages, Briles said.

Briles said teachers and students are "still coping with the situation of losing two students. I don't think it's something that is gonna go away in a month's period of time. I think it's something that's going to have a lasting effect on [the school community]."

Briles said students and teachers also appear to be angry that the suspect is still on the loose.

"They went through that shock and that horror," Briles said, and "now I think they're at a point where they're at an anger level. ... We know that the state police, the FBI, the local police, everyone, is doing everything within their power to capture the monster or monsters who did this ... but they're still angry."

Last week, Briles told ABC News that, as the school district's leader, he has not had time to process his own grief. Today, he said he has still "not slowed down." Next week is spring break, Briles said, so he hopes to find time to reflect then.

People can provide information by calling the tip line at (844) 459-5786. Information can be reported anonymously. Tips can also be emailed to abbyandlibbytip@cacoshrf.com.