For years, scores of teenage boys across the Midwest couldn't put a face or a name to the source of their torment: a man who distributed their nude images across the internet and even goaded some into sexual activity.

But on Tuesday, two of the young men sat in a federal courtroom in St. Paul as Anton Martynenko was sentenced to 38 years in prison for running a massive sextortion scheme described as the largest child porn production case ever prosecuted in Minnesota.

"We all can now be given freedom from this," said one victim, identified in court only as Grant, after the sentence came down.

Martynenko, 32, of Eagan, pleaded guilty in January for his role in a scheme prosecutors said victimized more than 155 boys — mostly high school athletes between 14 and 16 — by using fake social media profiles, often posing as young women, to persuade them to send him nude photos and videos, which he later would post online.

In passing sentence, U.S. District Judge Richard Kyle gave Martynenko two years' credit for his assistance to investigators on the Jacob Wetterling case. Martynenko shared information he picked up from suspect Danny Heinrich while the two were jail cellmates.

Martynenko scoured high school sports websites for the names of teenage boys, then tricked them into swapping sexually explicit photos and videos.

Some victims believed they were exchanging flirtatious messages with attractive young women, who actually were invented by Martynenko on one of the several "decoy" social media accounts he created. Other times, he hid behind social media profiles meant to look like a local high school hockey player and offered to pay victims to allow him to perform oral sex on them.

Once Martynenko obtained the images, he threatened to post them online — and often did — and shared them with dozens of classmates as a way of pressuring and embarrassing his victims.

Assistant U.S. Attorney Carol Kayser called Martynenko a "tenacious predator" who persisted in his four-year scheme even after interacting with local and federal law enforcement agencies.

Prosecutors said Martynenko lured at least three boys into performing sex acts on him, and that two of his victims later committed suicide.

"We don't know what role his scheme had [in their deaths] but you can certainly imagine the depression and stress this added to their lives," Kayser said.

Other victims like Roy, now 21 years old, spoke in court Tuesday. They said they also considered suicide as a result of "crippling anxiety" from having nude images posted across social media for friends, family and employers to see.

"My life has become a living hell," said Roy, who was 17 when Martynenko first messaged him.

Target lists

Grant was 15 when Martynenko reached out to him in 2012 purporting to be Cortney Jansgen, an attractive young manager of a modeling agency who pitched Grant on a $1,000 modeling gig. But first, Grant said, he had to share nude photos for a sample portfolio. Those images later circulated online after Grant turned down a request from another Martynenko account offering $300 for oral sex.

The images "spread like wildfire," Grant said, and he later spent sleepless nights trying to keep up with the latest social media alerts notifying that he had been tagged in another photo. Martynenko, Grant said, "was a terrible human being who spent years of his life making hundreds of teen boys miserable."

"It's an honor to be able to be here to speak for them," Grant later said of the many other victims who couldn't attend Tuesday's hearing. "I'm now going to enjoy my time without any fear of another attack. It's good to know that he's going to be unable to do that to us anymore."

Investigators from suburban police departments that also worked the case attended Tuesday's hearing, which spanned several hours.

The investigation began with a call from a Rosemount teenager to local police and eventually expanded to include the FBI. Martynenko was arrested in November 2015, minutes after sending his final Twitter message to a Minneapolis officer who was granted permission to operate a teen victim's account undercover.

Authorities eventually unspooled detailed "target lists" of teenage boys that Martynenko sought to contact. In court Tuesday, Kayser showed the judge one list and a screenshot of some of the meticulous folders of boys' photos that Martynenko organized by name, age, school and occasionally penis size.

In an interview after Martynenko's sentencing, U.S. Attorney Andrew Luger underscored the importance of using the internet safely.

"One of the things that keeps me up at night are the actions of a man like Anton Martynenko," Luger said. "This case highlighted how deeply disturbing the criminal obsession of a man like Martynenko can be. How not only does he steal the innocence of teenage boys but through extortion, threats and physical acts he inflicted unspeakable psychological damage to his victims."

A forensic psychologist who examined Martynenko testified Tuesday that he appeared amenable to intensive psychosexual treatment for addiction to pornography and other mental health problems. But he voiced concern at nearly 200 pages of chat logs between Martynenko and victims in which he expressed delight at "exposing" victims' nude photos.

His mother, Natalie Martynenko, who also addressed the judge during the hearing, embraced emotional relatives and supporters after hearing her son's sentence. She acknowledged that her son's crimes were serious, and said she had hoped for a sentence heavier on treatment than it was on incarceration.

"He's my only child," she said in the courthouse lobby.

A tearful Martynenko meanwhile apologized to victims in court, calling his own actions "disgusting," but arguing that he is "not an evil person trying to ruin lives."

He described his online activities as a "getaway" from anxiety and depression but "I literally couldn't have handled myself any worse than I did."

"I have to pay for what I've done," Martynenko said. "I'll do anything the rest of my life to make it up."

Kayser argued that Martynenko still failed to take full responsibility for his actions, including denying sexual activity with a third victim and maintaining he did not post some of the messages.

Marsh Halberg, an attorney for Martynenko, sought the mandatory minimum of 15 years for the three child pornography charges to which his client pleaded guilty. He argued that 40 years was essentially a life sentence.

"This will always follow him no matter what he does," Halberg said.

Twitter: @smontemayor