Transcript for College student uses gender swap filter to catch criminals
Otezla. Show more of you. We are back with a Snapchat a college student disguised himself with filters and caught a police officer charged with being a predator. Amy has details. Incredible story. The student says he used the gender swap filters to crack down on people accused of preying on underage girls. They're the wildly popular Snapchat filters that swap a person's gender with a quick tap going from he to she or vice versa in an instant but this morning, one California college student says he used the filters to try and help others avoid the suffering his friend faced when she was assaulted. It turned out that with the gender filter I made a very pretty girl so I decided to take advantage of it and try to make a tinder account to catch some Pell files. Reporter: Ethan says he created the account as a 19-year-old female named Esther meeting the 18-year-old minimum age requirement and says he matched with a 40-year-old man and moved their conversation to the messaging app kik where he made his female persona even younger. He asked me to tell him about myself. I told him my name is Esther as you know and I'm 16 and like comic book movies and "Star wars." Reporter: That man, San Mateo police officer Robert Davies sent these messages saying Esther's age might be an issue but Ethan says after that they became explicit. He talked about all the things he wanted me to do to him and what he wanted to do to me. Reporter: That's when the 20-year-old alerted silicon valley scream stoppers of the conversations. It led to Davis' arrest charged with contacting a minor to commit a felony. The Santa Clara county deputy district attorney telling ABC news we will work hard to hold this defendant accountable adding we do not recommend members of the community attempt to investigate these matters on their own. There are officers who are well trained to investigate these crimes. As for Ethan he says Esther will no longer be swiing right. After I talked to police I deleted the account. What an incredible find he had. Dave Visa is currently out on paid administrative leave and the police chief saying this alleged misconduct if true is no way a reflection for all that we stand for as a department. I understand why it's not recommended but it's still pretty remarkable what this young man was able to do. Yikes. No question about that.
This transcript has been automatically generated and may not be 100% accurate.