In the early hours of Dec. 3, 2016, 19-year-old Sarah Stern's 1994 Oldsmobile Eighty-Eight was found abandoned on a bridge between Neptune and Belmar, New Jersey, keys dangling from the ignition inside.
From appearances, it seemed to be suicide. The car had not been broken into and there were no signs of a struggle. Dive teams searched the river below, while helicopters skimmed the shores. But there was no sign of her. That wasn't unexpected, though. Had she fallen into the fast-moving currents below, she would likely have been quickly swept out to sea.
Her friend from childhood, Liam McAtasney, provided support for the suicide theory. “I just know she’s been trying to get away, been telling me she’s moving to Canada,” McAtasney told police at the time, according to the Asbury Park Press.
She had attempted to take her life once before, police said he told them. Her mother had died from cancer a few years earlier and she'd been arguing with her father recently, he claimed.
She had every reason to want to end things, McAtasney said.
But two months later, the case took a sudden turn. In February 2017, McAtasney was arrested, accused of strangling Stern over the course of 30 minutes, which he had brutally detailed in a secretly recorded confession that authorities said broke the investigation wide open.
What happened between these two lifelong friends?
Anthony Curry, 21, was good friends with McAtasney, with whom he attended high school, he told ABC's "20/20" as part of a special set to air Friday. They both loved movies and McAtasney, also 21, would often give Curry ideas "about films I should make and all that stuff," Curry said.
In late November 2016, just days before Stern's disappearance, Curry said McAtasney told him a strange story. "He told me about this idea he had to kill this girl ... that he was going to strangle her and throw her over the bridge with his friend,” Curry said McAtasney said.
It was a gory plot, but Curry said he never for a second thought that McAtasney was discussing real life. "I just thought it was a movie," he said.
When Stern vanished, her car left behind on the bridge, Curry said he didn't question it. He only became suspicious once McAtasney began contacting him via Snapchat, asking him whether police had reached out to him.
Still, Curry didn't want to believe anything bad of McAtasney.
"Somebody who's your good friend, you don't think they would do something like that," he said. But then Curry started to worry about his family. "If somebody is capable of doing that, he could try to hurt my family or somebody I knew ... kid’s wacko,” he said.
He ultimately contacted police in January 2017 about the conversation he and McAtasney had had in November, around Thanksgiving. They set him up with recording devices to see if Curry could get McAtasney to confess.
The resulting audio and video was the linchpin in the state's case against McAtasney. In it, McAtasney describes strangling Stern. “It took me half an hour to kill her,” he says.
The motive? A box full of cash that McAtasney said Stern had discovered her mother had left for her before dying of cancer in 2013.
McAtasney told Curry in the recording he thought it contained tens of thousands. But the real sum was much less, just around $10,000.
“The worst part of it is I thought I was walking out [with] $50,000 to $100,000 in my pocket,” McAtasney says. The cash, he adds, appeared "burnt or something." He says he was unsure a bank would even take it.
Speaking to "20/20," Curry said that McAtasney seemed relieved to talk about what happened. “He wanted to tell me. I think he wanted to get it off his chest. For some reason he trusted me,” Curry said.
McAtasney was arrested shortly afterward. He later denied he was talking about Stern's murder, claiming he believed he was auditioning for a movie.
The arrest came as a shock to Stern's father, Michael Stern.
"It's a feeling of hurt," Michael told the Asbury Park Press of learning that Sarah's friend had been arrested for killing her. "Emptiness. Just like being knocked over and then kicked. It takes your breath away. It's a horrible feeling. Indescribable. Pain. Suffering."
What made it worse was that Sarah's body had not yet been found.
And it still hasn't.
Arrested with McAtasney was his friend Preston Taylor, who was accused of helping McAtasney dispose of Sarah's remains.
Taylor, who was at one point Sarah's prom date, eventually pleaded guilty to first-degree robbery, second-degree conspiracy to commit robbery and second-degree disturbing or desecrating human remains, and agreed to testify against McAtasney at trial.
In his testimony, Taylor claimed that he and McAtasney took Sarah's body to the bridge in her own car after McAtasney killed her and then they both tossed her remains over the edge into Shark River in an attempt to make it appear as though her death was a suicide.
According to Taylor, McAtasney planned the murder for six months after first hearing about the cash. Initially, they planned to rob her, Taylor said, but eventually they decided the easiest way to make off with the money would be to kill her.
Friends and family testified that, contrary to McAtasney's claims, Sarah was a happy girl. Carly Draper, a friend of Sarah's, said at trial that the day she disappeared, she told her that she was planning to move to Canada with McAtasney. Draper didn't really believe her — Sarah had previously spoken about moving all over the country and never had — but she emphasized that Sarah appeared content.
"She seemed very happy and excited because she thought she was going to Canada," Draper said.
Sarah's aunt, Shirley Longo, testified that she too saw Sarah the day she went missing but she never mentioned wanting to move. And Sarah's cousin, Michelle Bahr, said she was "just happy-go-lucky Sarah" when she saw her two days before she vanished.
On Dec. 2, McAtasney finally carried out the plan, according to Taylor. McAtasney killed her at her home, then called Taylor for help. In so doing, he told Taylor about how Sarah had died, saying she tried to appeal to him while he choked her over the course of a half-hour.
“In the process, she beat herself, she vomited," Taylor testified. "When she started throwing up, he stuffed a scarf down her throat, and all the while, she said his name a couple times.”
McAtasney's recorded confession echoes this description. “I thought I was going to choke her out in a couple minutes," he says. "She was having a seizure on the floor. I got a shirt and shoved it down her throat so she wouldn’t throw up, and held my finger over her nose and set a timer.”
What McAtasney had been most concerned about, he says in the confession, was Sarah's dog. But it turned out he needn't have worried. “Her dog lay there and watched as I killed her," he says. "Didn’t do anything.”
When she was finally dead, Taylor said he hid her body under a bush, where it stayed for eight hours until he and McAtasney came back, loaded her remains into her car and drove to the bridge.
Though McAtasney was disappointed in the amount of money he received, he says in the confession that something was better than nothing.
“I didn’t get a lot of money, but I got enough to live comfortably in my house and throw parties all the time,” he says.
At one point, the trial was nearly thrown into jeopardy when a juror was tossed from the jury for writing an inappropriate Facebook post. "Sitting on the jury LMAO [laughing my ass off]," the post read. McAtasney's lawyer insisted a mistrial be declared in the wake of the comment, but the judge threw out that request and proceedings moved forward.
For the defense, McAtasney's lawyer, Carlos Diaz-Cobo, raised questions over whether Sarah was indeed dead, calling witnesses who said they saw Sarah hours after she'd been killed were called to speak in McAtasney's defense. McAtasney himself did not testify.
Among them was a witness who testified that he saw Sarah walking down the street around 5 a.m. on Dec. 3, which would have been after the time prosecutors say she was killed. He added that later he saw a disabled car on a bridge down the road. However, investigators said the car in question had been towed from the bridge hours earlier, undermining the witness' testimony.
Ultimately, McAtasney was found guilty on all counts Tuesday. His sentencing is set for May.
The verdict brought tears to the eyes of Sarah's father, Michael.
“The most important thing is to get justice for Sarah,” he told reporters after the decision was announced. “She was a great kid, and this never should have happened liked this.
"Sarah's up in heaven," he added. "She's an angel, and she was just a beautiful person. She never had a mean bone in her body."
But Diaz-Cobo said he plans to appeal the decision, adding that McAtasney was very upset despite the fact that "there were no tears coming out of his eyes."
Speaking to "20/20," Michael credited Curry with helping solve the case.
"We probably never would have got an answer" to what happened without Curry, said Michael. "... It was a tough decision for him. He didn't have to come forward."
Michael also spoke candidly about the sense of relief he felt when McAtasney was declared guilty. "I didn't hear anything after that [word]," he said. "I don't know what happened. I heard voices talking, but guilty, that's all I needed to hear."
Asked what he would tell McAtasney now, Michael replied: "You're an evil person. You shouldn't exist on this earth."