A few weeks later, another Belmont High girl showed up at the police station. A guy was harassing her too. Moulton thought the cases were unrelated. But then more girls came in, many describing similar stories and a harasser named Seth Williams. Some were ashamed, some in tears, some accompanied by furious parents.

Moulton had an epidemic on her hands.

The victims had one thing in common: They all had attended Belmont High. Cole Wilson; Embroidery by Diane Meyer

In 2011, May was a 16-year-old who had spent most of her life in Belmont and was living with her mom and two siblings in a duplex with a nice yard. Then, midway through her sophomore year at Belmont High, her family moved to a nearby town and she enrolled in a new school. She barely knew anyone. “I wasn’t that popular, I guess you could say,” May said. So when she got a Facebook friend request from someone named Seth Williams, who had a cute profile photo, she accepted it.

Seth started messaging May frequently, making idle conversation, and after they exchanged numbers, he began texting. He said nice things and seemed to want to get to know her. He’d ask about her favorite ice cream flavor and her pets. She enjoyed the back and forth. When he asked for photos of her body, she hesitated at first but talked herself into it. “I still was like, no guy shows me this attention,” she told me. “He actually seems like a nice guy. Maybe it’ll be OK.” May sent him a photo she thought was fun, of her rear in jeans, plastered with handprints from her freshly painted room. He wanted more. She sent him a picture with her in underwear, then one of her bare butt. When he demanded a full nude, she told him, “No. That’s where I draw the line.”

No picture, no Facebook, he replied. When May next tried logging in to her accounts, she couldn’t access them: He’d hacked her Facebook and her email and changed the passwords. She begged him to return the accounts; he refused. She blocked him on her phone; he texted from a different number. She changed her number; he still found her. “He always came back,” she said. “Always.”

By April 2012, Seth had escalated his threats. Citing the “ass shots” May had sent, he wrote to her: “If you don’t send me a nude by 8, Im sending this picture to people and uploading them to Facebook.”

“Get off my FB,” she responded.

“Take your clothes off.” “Get fucking naked on camera.” “I’m going to have fun fucking you this summer,” he replied.

May didn’t send a naked picture, and Seth retaliated by using fake Facebook accounts in her name to message her friends at her new school. Friends became jumpy, and their parents did too, forbidding them from hanging out with May. “I never felt so alone in my life,” she said.

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Seth would disappear for a while but then resurface, finding May even as she went through a slew of phone numbers. She trusted only those few friends who’d stood by her. If she was home alone, she locked the door to her bedroom. Strangers made her tense up. “You could be crossing somebody in the road,” she said, “and you don’t know if that’s the person you’re messaging.”

By the fall of 2012, Seth had been silent for a while, and May thought maybe, finally, he had decided to stop bothering her for good. But one night, while she was sitting in her living room, a text pinged on her phone. It was Seth. “I just felt like I lost hope,” May said. He was again demanding pictures. This time, though, the text included nude photos of other girls.

In one of the images, May recognized a close friend from her Belmont days. Seth had bragged that he had photos of this girl, but May hadn’t been able to bring herself to ask the friend about Seth. “I was very ashamed of myself,” May said, “and I was very upset about what I had done” by sending explicit pictures. Now, with the photo in her possession, she called her friend, thinking maybe she would have advice. The conversation was brief. They didn’t break down or comfort one another. But May’s friend did urge her to talk to her mother and go to Detective Moulton in Belmont.