The FBI-MPD Child Exploitation and Human Trafficking Task Force arrested a Silver Spring, Maryland, man in D.C. on Friday who’s accused of sharing child pornography on social media.

In an indictment, unsealed Friday, Joseph Ruben Baer, 20, was charged with one count of distribution of child pornography.

The task force said they were monitoring a social media app because they believed pedophiles were using it.

According to the U.S. Attorney’s Office for D.C., an undercover agent monitoring the app began messaging with Baer on April 18. Baer “expressed an interest in the sexual exploitation of prepubescent boys” and later sent the agent two video files on the app that showed him “masturbating while watching child pornography on a laptop computer.”

Days later, on April 25, a federal grand jury returned an indictment charging Baer.

The task force executed a search warrant on Friday at two residences connected to Baer in Silver Spring, but he was picked up in The District.

Baer first appeared in court later that day. He is being held without bond.

The case remains under investigation, the U.S. Attorney’s Office for D.C. said. It’s being pursued under Project Safe Childhood, launched in May 2006 by the Department of Justice. Project Safe Childhood is a national strategy to combat child sexual exploitation.