The sheriff's deputy paces slowly at the foot of the school auditorium stage, a gold badge pinned to the pocket of his polo shirt, a gun holstered at his hip. His expression is sombre.
He would look right at home leading a DARE or gang-resistance program, warning teenagers against ruining their lives with drug use or street crime.
But his audience members this morning are fidgety, pint-size 11- and 12-year-olds, and his warnings are about the threats lurking in their laptops and gaming devices and smartphones - such as grown-ups who send messages or photos to kids they don't know, trying to get them to respond. Child abusers have a name for this technique.
"They call it bunny hunting," the deputy says, and the hundred-or-so tweens sitting before him grow very quiet.
The original version of this class was offered only to parents, with an emphatic content warning.
But as perils like sexting, sextortion, cyberbullying, sexual predation and identity theft have grown, the sheriff's office in Loudoun County, Virginia, expanded its outreach to include sessions for sixth-graders and ninth-graders - the kids transitioning to middle or high school, still figuring out how to navigate their teen years, even as the devices in their pockets place a world of adult content and consequences at their fingertips.
And so the deputy, Sgt. James Spurlock, a 26-year law enforcement veteran who oversees the sheriff's Crime Prevention and Juvenile Resource Unit, has come to Stone Hill Middle School in Ashburn, Virginia, to lead a program called "Technology Safety for Teens"- an anodyne title that belies its disturbing material - because cops know that the need to teach kids about sexual exploitation online starts younger and younger.
Spurlock begins by asking the middle-schoolers a question.
"If someone threatened you online or sent you something inappropriate, how many of you would immediately go tell your parents?"
Several dozen kids raise their hands right away. A few of their classmates visibly hesitate, then do the same. Other students sit with their arms pinned firmly to their sides.
"OK, not everyone's hand is up," Spurlock says. He doesn't sound surprised. "So let's talk about that."
Educating young people about the dangers of the digital realm has become a growing priority for law enforcement agencies and schools nationwide. Some jurisdictions use specific curriculum or training programs - i-SAFE, a leading technology safety training program employed by officials in the United States, is used in 4,000 school districts across the country - while others conduct their own outreach.
Spurlock has been leading Loudoun's technology safety classes since they began in 2012. He always tells the students that he's not only a cop, but also a dad, and also a weapons designer for the video gaming industry (the Stone Hill crowd is impressed by this revelation). His goal is to connect with kids and leave a lasting impression, which means he doesn't sugarcoat the material.
And he also wants to hear what the kids have to say. So he asks the Stone Hill students why they wouldn't tell their parents if something upsetting happened online - a friend was mean to them, or a stranger contacted them, or someone asked them to send a picture.
"They might take away your phone," one girl says.
"You might just think it's a joke," another girl says.
"Maybe you think you can just handle it yourself," a boy volunteers.
Spurlock explains how important it is for kids to tell an adult if something - anything - makes them feel unsure or uncomfortable online. When he teaches these classes to parents, he says, he always tells them that they shouldn't get angry or punish a kid for telling the truth.
After all, their parents are probably the ones who brought them into the digital world, posting childhood photos and videos. "For most of you, your internet presence started long before you touched your first device," Spurlock says.
A few rows back from the stage, two girls are raptly focused on a paper fortune-teller game.
The session is about an hour long and slightly gentler than the version presented to parents; Spurlock doesn't tell the students about the worst cases - the ones where a teen committed suicide because of bullying, or a child was killed by someone who stalked them online. He avoids mentioning the lives cut short, focusing instead on those who were irrevocably changed.
Like Cassidy Wolf, a onetime Miss Teen USA whose laptop webcam was hacked by a 19- year-old student who took nude photos of her: "Forever, this will follow her, because there's no way to know where those pictures went," Spurlock says. Or Axelle Despiegelaere, a pretty Belgian teen who lost a lucrative modelling contract with L'Oreal after a photo of her posed with a hunting rifle beside a dead oryx antelope surfaced online.
He tells them about a girl who posted a photo online with a "geotag," which meant that an online stalker figured out where she lived and showed up on her front porch. He talks about voice-modulating software that can disguise someone's age and gender - adults often use it when they contact kids through video games. There is a large community of predators out there, he says, and now the two girls with the fortune-teller game are staring at him.
In a recent case in Loudoun, investigators arrested a man who had used Skype to send sexual solicitations to more than 70 children. The man was a government official, Spurlock says, making the point that predators are often seemingly trustworthy figures: "Judges, law enforcement officers, teachers," he says. "It's not the creepy old guy in the basement."
A girl with a curly ponytail raises her hand. "Why would someone work so hard just to hurt a kid?"
For the first time, Spurlock hesitates for a moment. He explains that predators have a range of motivations - "every person is a little different" - but offers no specific examples.
He changes the topic, focusing next on what kids can do to protect themselves. Dozens of iPhones are pulled out of pockets when Spurlock explains how to disable the geotag function on Instagram and check that their accounts are set to "private" instead of "public." He explains that they should never share their family's wireless router password with anyone else (about a dozen raise their hands to admit they already had).
He also reminds the students that they themselves could be considered predators: "If you have nude pictures of a person under the age of 18, you are going to prison," he says. "How old do you have to be in Virginia to be prosecuted as an adult?"
A confident chorus answers: "Eighteen!"
"Fourteen," Spurlock says. This gets the reaction he was looking for; the kids gawk and gasp.
"I know this might all seem unbelievable," he says, "but don't ever think it can't happen to you."
He surveys the grim-faced children in front of him and recites a statistic from a 2014 FBI report about children between ages 12 and 18 who receive unwanted sexual solicitations online.
"One in five of you will be a victim before you turn 18," he says. He repeats: "One in five."
The room is mostly quiet. Some tweens stare at their phones, or at the wall-mounted clock over the auditorium door, ticking down the final minutes of the school day.
Others glance uncomfortably each other's faces, doing the math, wondering when and how and who.