Classmate: N.J. Teen Sarah Stern was 'Super Close' with Two Boys Charged with Her Murder

The friend tells PEOPLE that Sarah Stern called the childhood friends charged in her death "her 'besties'"

Two close friends of a New Jersey teen who hasn’t been seen since early December are charged in her death — and a former classmate of the trio tells PEOPLE the suspects “would have literally been my last guess.”

Prosecutors allege Liam McAtasney, 19, told a witness he choked 19-year-old childhood friend Sarah Stern and watched her die for “about 30 minutes.” McAtasney then allegedly called Preston Taylor, also 19, and the pair dumped Stern’s body in the Shark River, abandoning her car with the keys still in the ignition.

Speaking exclusively to PEOPLE, Morgan Randle, a friend of Stern’s, says Stern, McAtasney, and Taylor “were like best of friends. Literally, you saw one of them, you’d see the others.”

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“It was Sarah, Liam and Preston,” Randle adds. “They ate at the cafeteria together … and they would put their stuff in each others’ lockers. The knew each others’ locker combinations, and they could grab books for each others’ classes because they knew each others’ schedules. They were that close. She called them her ‘besties.’ ”

Randle says “there wasn’t anything romantic” between the trio, even though Stern and Taylor went to the prom together. He adds that “they weren’t the most popular kids at school, but they weren’t outcasts either.”

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When Stern’s car was found abandoned on a bridge near her home on Dec. 3, it wasn’t surprising to Randle that her two close friends joined the search for her.

“He posted a lot of things [to Facebook] like, ‘I’m looking for my best friend. Please help me find her,’ ” Randle says. “It made total sense. They were her best friends.”

He adds, “If they’re responsible for doing this, if they killed her, that makes it even worse. The betrayal? That’s devastating.”

McAtasney is charged with first-degree murder and Taylor is charged with disturbing human remains and hindering prosecution.

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Both McAtasney and Taylor are being held without bond. Neither has entered a plea.

McAtasney’s attorney, Charles Moriarty, tells PEOPLE his client “is completely innocent.” Moriarty also says there’s no proof Stern is even dead.

An attorney for Taylor did not return PEOPLE’s call for comment.