NBC Bay Area, Screenshot / NBC Bay Area

A California college student used Snapchat's gender-swapping filter to pose as an underage girl online in order to catch sexual predators — leading to the arrest of a 40-year-old police officer.



Robert Edward Davies, an officer with the San Mateo Police Department, was arrested Thursday on suspicion of contacting a minor to commit a felony, the San Jose Police Department said in a statement.



Davies allegedly chatted about sexual activity with the fake profile despite being told "she" was underage. The police department referred to the person who created the profile only as a "concerned citizen."



In an interview with NBC Bay Area on Tuesday, the student, who said he only wanted to be identified by his first name, Ethan, said that he purposefully posed as an underage girl online to catch sexual predators. He was inspired to do so after learning that a close friend had been molested as a child.



On May 11, police said the "concerned citizen" took a selfie with Snapchat's new gender-swapping filter and created a Tinder account as a 19-year-old. The dating app requires all users to be 18 or older, but police said the photo appeared to be of a younger girl. Ethan told NBC Bay Area that a man named "Rob" reached out over Tinder soon after the fake profile for the girl, whom he named "Esther," went up.

"I believe he messaged me, 'Are you down to have some fun tonight?' and I decided to take advantage of it," Ethan said.

Screenshot / NBC Bay Area

The student asked Davies to switch to the messaging app Kik, where, posing as "Esther," he informed the older man that "she" was only 16. Davies acknowledged the information, but continued the conversation, according to police.



The police officer eventually allegedly asked that the two move their communications over to Snapchat.



"We started texting on there, and it got a lot more explicit," Ethan said. Per police, Davies and "Esther" talked about "engaging in sexual activity."



Following the Snapchat messages, Ethan said, he took screenshots while his phone was on airplane mode, so as not to alert Davies that the communications were being documented.

Handout / San Jose Police Department