ST. JOHNS COUNTY, Fla. -

Prosecutors said a St. Johns County man is behind possibly the largest case of sexual extortion in the United States.

Court records allege 30-year-old Lucas Chansler solicited nude pictures and videos from more than 200 underage girls and then threatened he'd spread them unless they sent him more. The crime is known as “sextortion.”

Chansler was arrested in 2010 but hadn't stood trial because his attorney argued he was not competent, because he suffers from severe anxiety and depression.

Now a federal judge has decided Chansler is competent to stand trial at the end of this month.

According to records, Chansler admitted to preying on teenage girls over the Internet and then threatening to spread the files he recorded of them all over the world.

There are hundreds of pages of court records accusing Chansler of a number of sex crimes, which federal agents said he committed from his home computer.

According to his indictment, Chansler went online and “at first pretended to be a friend, acquaintance or admirer of the minor victim addressees on social networking websites such as MySpace and Facebook."

He pretended to be a teenage boy and would ask them to video chat. That's when Chansler would put up fake video of a teen boy and ask the teen girls to expose themselves and perform on camera. But they didn't know Chansler was actually behind the computer.

According to the indictment, "this conduct would be recorded by Chansler, and then he would send a copy or portion of the video recording to the minor victim. If she did not comply with his demand, he would injure her reputation by sending the sexually explicit images and videos to her friends, or by posting the images or videos to a public website."

Prosecutors said he did this from 2007 to 2010, when the FBI arrested him. Thursday the Feds said they've identified more than 200 underage female victims, making it likely the largest case of "sextortion" in the United States.

“People that do this, practice it, they take tips from the dark web,” said Christopher Hamer, network administrator for the Bradford County Sheriff's Office. “There are forums that have chips and applications that they can use to make it easier.”

Hamer is the computer guru for the Bradford County Sheriff's Office. He said the Internet can be a scary place, and this is a lesson for parents to talk to their kids about dangers like "sextortion."

“Not to do things on the computer that you would not want your mother or father to see,” Hamer said. “Because if you are doing something that you wouldn't want us to see, the moment it leaves your control it is gone.”

Chansler's trial is set for Aug. 25. Since his arrest, he has spent his time at a federal institution in North Carolina.

Over the course of four years, several psychologists have examined him. They said he's very intelligent. He was in a master's program for pharmacy.

One expert said that Chansler broke down crying when he was talking about what he did to his victims.

Alan Rosner, Chansler's defense attorney, said Thursday that "we do not comment on pending litigation."

The Department of Justice also declined to comment because the case has not been decided.