"There was a talk of baby dying but no one knew what happened," says Misty Bergmann. "Not until last week."

A neighbor of the Iowa couple who have been charged with murder after their 4-month-old son was found dead in a motorized swing in August tells PEOPLE the horrific allegations have rattled residents of the small town of Alta Vista.

“It was absolutely shocking,” Misty Bergmann says. “It’s just hard to believe.”

Cheyanne Harris, 21, and Zachary Koehn, 28, were taken into custody on Oct. 25. Both have been charged with child endangerment and first-degree murder in the death of their son, Sterling Koehn, according to a criminal complaint obtained by PEOPLE.

Neither has entered a plea to the charges, and their attorneys could not be reached for comment. They are being held without bail, and both are due back in court on Nov. 2.

Court records allege that police and medical personnel were summoned to the couple’s apartment on August 30. Koehn had called 911 that day, requesting an ambulance for his unresponsive son.

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Authorities arrived to find the lifeless boy in the swing, the complaint states. Medical examiners would later discover “maggots in various stages of development” in Sterling’s “clothing and on his skin.”

Bergmann says that before the allegations became public last week, she’d heard very little talk around Alta Vista about the case, but knew detectives were continuing with their investigation into Sterling’s death.

“We’re a small town so when it happened, we had all these cop cars racing into town and everyone’s trying to find out what’s going on,” she says. “There was a talk of baby dying but no one knew what happened. Not until last week.”

Cheyanne Harris and Zachary Koehn
Cheyanne Harris and Zachary Koehn
| Credit: AP/REX/Shutterstock

Bergmann says “no one knew” how the baby died, but “you figured it had to be something big, because if it was just that a baby died, it would have been reported on the news right away. But it wasn’t.”

Instead, for two months, Koehn and Harris continued to live in Alta Vista, a town with no traffic lights that measures less than half-mile long.

Bergmann, who moved to Alta Vista back in April, tells PEOPLE she met the couple only once, as she was making her way to work; she only exchanged hellos with them.

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“They were living their lives,” Bergmann says. “I just don’t know how they thought they could pass something off like that?”

Authorities believe Sterling, who weighed less than five pounds at death, was left in the baby swing for over a week, and that he was not bathed or changed that entire time.

The cause of death has been ruled a homicide, and the manner of death was failure to provide critical care, according to court papers.

“The facts of this case go far beyond neglect and show circumstances manifesting an extreme indifference to human life,” Chickasaw County Sheriff’s Deputy Reed Palo wrote in the criminal complaints.