WARNING: This story may be disturbing to some readers.

Richard Allen confronted Abigail Williams and Liberty German with a gun before killing the teenage girls on a hiking trail in Delphi, Indiana, on an unseasonably warm day in February 2017, prosecutors said Friday.

During opening arguments in the Delphi murder trial, Carroll County Prosecutor Nick McLeland said the state's case focuses on the man on the Monon High bridge, an unspent bullet found at the crime scene and the murders of Abby and Libby.

McLeland claimed Allen encountered teenage best friends Libby, 14, and Abby, 13, and then used “power and fear” to force them “down the hill” before cutting their throats . After the girls crossed a bridge, the prosecutor said they saw a man behind them, after which Libby started a recording on her phone at 2:13 p.m

Derrick German, Libby's father, went to pick up the girls that afternoon, but they weren't there, he said.

When the girls' bodies were found the next day after they were reported missing, 14-year-old Libby was naked and covered in blood, while 13-year-old Abby was wearing Libby's sweatshirt and jeans and had thrown other clothing into a stream, according to reports the prosecution told jurors.

Allen hid in plain sight for years, prosecutors said.

“The last face the girls saw before their throats were cut was Richard Allen's face,” McLeland said.

In his opening statement, defense attorney Andrew Baldwin said the state's case was built on a flawed timeline and inconsistent evidence. He highlighted witness statements and forensic evidence that cast doubt on the state's case.

Baldwin insisted the state's investigation had been “messed up from the start” and accused the state of “losing interview after interview that we'll never see.”

“We want the truth to come out in this courtroom for the families,” he said.

Baldwin told jurors that the prosecution's case “will fall apart before your eyes” when they see the phone data evidence.

The defense also tried to discredit the prosecution's claim that the bullet found near the girls' bodies belonged to Allen. Baldwin said law enforcement typically uses the type of bullet found at the crime scene, but police never investigated whether an officer was missing a .40 bullet. He also said that the owner of the property where the girls were found owned a .40 caliber gun, but his gun was never tested to see if it matched the bullet found.

Baldwin said an expert will testify that the markings on the lab's test bullet were “insufficient” to match Allen's gun to the bullet at the crime scene.

Baldwin also stated that the state's timeline does not match the time Allen was on the trail. He called two witnesses who reported seeing a man in the area who looked nothing like Allen. Baldwin said if the timeline and witness statements don't match those of the prosecution, the case “falls apart.”

Baldwin said Allen told his family, “Maybe I'll just confess all this so you don't have to suffer.”

Below you will find partial statements from witnesses made on the first day of the trial:

Second state witness: Kelsi Siebert, Libby's older sister

On the morning of the murders, Kelsi said Libby “asked me to go to High Bridge. She wanted me to go with her.”

Kelsi said her grandma called sometime after 4 p.m. to tell her Libby was missing. Kelsi and her boyfriend tried to reach Libby, WTHR reported.

The family met and walked across the high bridge. Prosecutors had Kelsi show her route on a satellite map. She crossed the left side of the path. They went north from the bridge, where there was a hill to go down, and then went west, where there was a gate.

Kelsi said there was a tree along the route with shoes on it, but that wasn't a concern. According to Kelsi, “a lot of kids” put their shoes on the tree.

“Did you think something bad happened?” asked Assistant District Attorney Stacey Diener.

“No, we thought they were out in the woods somewhere,” Kelsi said.

Kelsi said she would text with Libby a few times, but most of the conversation was on ShapChat.

“She would have sent a picture with words,” Kelsi said. “If you didn’t save it, it would disappear in a few hours.”

Kelsi remembered Libby posting a picture of the bridge and then a picture of Abby on the bridge.

Kelsi didn't return to the trail after the first pass with her family, but said, “I texted her and called her.”

When they returned, Kelsi said, “We were divided into groups. My group crossed the High Bridge. We went down and to the right. We looked under the bridge.”

Kelsi became emotional on the witness stand as she said: “Shortly after, someone called out that they had found the girls.”

The state's first witness: Becky Patty, Libby German's grandmother

According to Becky Patty, the girls did not have school on February 13, 2017 because it was a scheduled snow painting day that was not necessary.

Becky said Abby stayed at her house the night before the murders – and Derrick, Libby's father, made them breakfast the next morning.

Becky said the last thing she said to Libby was to put a jacket on, to which Libby replied, “Grandma, I'm fine.” Becky wiped away tears as she recounted this.

Becky said Derrick called her around 3:30 p.m. because the girls weren't at the pickup location and Libby wasn't answering the phone. She also said Abby didn't have a cell phone.

Becky then called her husband Mike and said she was worried and wanted to search the trail for the girls. Becky said she also called AT&T to see if they could ping Libby's cell phone.

Around 5 p.m. Becky told Mike to call the police because it was getting dark. Becky said she then called Anna Williams, Abby's mother, to tell her the girls were missing.

“We called. We kept calling,” Becky said with tears in her eyes.