How 2 teenagers plotted their best friend's murder

When 16-year-old Skylar Neese went missing from her West Virginia home after midnight on July 6, 2012, two of her best friends took to social media to express their fears and hopes that Skylar could be alive.

But months later, investigators would find out that Rachel Shoaf and Shelia Eddy were hiding a sinister, deadly plot behind their posts and were ultimately responsible for Neese's death.

"We asked Rachel, 'Why did you guys kill Skylar?' And her only answer to that was, 'We just didn't like her,'" State Police Cpl. Ronnie Gaskins told "20/20."

An all-new "20/20" episode airing Friday, April 12, at 9 p.m. and streaming on Hulu the next day explores the case with fresh insight from investigators, a group of journalists who profiled the murder in a new podcast "Three," and others.

The three high school sophomores, who lived near Morgantown, West Virginia, used to be inseparable, according to Neese's parents.

Neese and the two other girls had their ups and downs; around the time of Neese's disappearance, the three had been feuding, according to investigators.

In the days leading up to her death, Neese's Twitter account showed that something had gone awry.

On July 4, 2012, two days before she was murdered, Neese tweeted, "It really doesn't take much to p--- me off," and, "Sick of being at f------ home. Thanks 'friends,' love hanging out with you all too."

The day before she was killed, Neese tweeted, "you doing s--- like that is why I can NEVER completely trust you."

After Neese went missing, Eddy told Neese's mother that she, Neese and Shoaf had been driving around town that night getting high before Neese went missing. Eddy claimed she and Shoaf had dropped Neese off at the end of the road from her apartment building so that Neese could sneak back in.

The two girls told investigators they picked up Neese at 11 p.m. the night she went missing.

Eddy posted regularly on Twitter about her thoughts and day-to-day activities as authorities searched for her "missing" friend. Eddy also posted about her friendship with Shoaf.

But as the investigation into Neese's disappearance continued, with the FBI ultimately getting involved, suspicion mounted that the girls were harboring a secret.

Upon a review of surveillance video that showed Neese being picked up by a car at 12:30 a.m. the night of her disappearance, law enforcement realized that the victim's two friends lied in their original statements to police.

Video footage from a nearby convenience store as well as cell phone records confirmed holes in the two friends' story. Investigators said they knew they had lied, but had no idea what they were hiding or why.

Suspicions mounted and the community was divided in their support of Shoaf and Eddy's claims.

A few months after Neese's disappearance, Shoaf suffered a nervous breakdown following weeks of probing by investigators. On Jan. 3, 2013, she confessed to investigators that she and Eddy had stabbed Neese to death.

Judge Perri Jo DeChristopher, who helped investigate the case when she was an assistant prosecutor, told "20/20" that her office was skeptical about Shoaf's confession.

"If one co-conspirator gives a statement against another co-conspirator, you really have to use it as a starting point to corroborate the facts," she said.

However, Shoaf gave information that led authorities to Neese's remains, which were found in a wooded area over the Pennsylvania state line, about 20 miles from Star City, West Virginia.

During her January 2013 confession, Shoaf had told authorities how she says she and Eddy had planned Neese's murder.

The plan was to pick up Neese from her house at night and drive to a remote area to smoke marijuana. Once they were in the woods, Shoaf said the plan was to count to three, then stab Neese to death. Authorities say that Neese was found with over 50 stab wounds.

Attempts were made by investigators to get Eddy to incriminate herself, including having Shoaf wear a wire, but they were unsuccessful.

Eventually, investigators conducted a search warrant of Eddy's house and confiscated her computer, phone, and tablet, knives from the kitchen and a car from the residence -- a Toyota Camry.

An FBI analysis of the car found Neese's blood DNA in the trunk of the vehicle. On May 1, 2013, Eddy was arrested in a restaurant parking lot. Both teens were charged with murder as adults.

Eddy pleaded guilty to first-degree murder for her role in the killing.

On Jan. 24, 2014, roughly 18 months after Neese's death, she was sentenced to life in prison.

Shoaf pleaded guilty to second-degree murder, a lesser charge based on her cooperation with authorities, and was sentenced to 30 years in prison the following month.

Only Shoaf apologized to Neese's parents during her plea deal.

"[Eddy]'s not sorry," David Neese told "20/20" in a previous interview. "You don't apologize for murdering somebody in cold blood because she meant to do it."

Shoaf was denied parole last year.

Neese's family, friends and others from the town said they are still numb from the wound left by her murder.

"Nobody wins. Skyler isn't around, the two girls are in jail, the two girls' parents are living through this, and Morgantown still is ripped apart because of this situation," Tom Bloom, a former guidance counselor at the girls' high school, told "20/20."