A man has been sentenced to 27 years in federal prison for blackmailing a 9-year-old girl into sending him naked pictures.

Larry Gutierrez, 50, of Bremerton, Washington, was sentenced this week in the U.S. District Court in Spokane for producing child pornography.

According to the U.S. Attorney’s Office, a mother found naked pictures of her 9-year-old daughter on the girl’s cellphone in 2014. The girl had been sending them to a man she met on Kik, a private messaging app.

The man, later identified as Gutierrez, sent the girl pictures of a young man’s body and claimed they were of him, the U.S. Attorney’s Office said. He asked her to send pictures of herself, and later threatened to share those pictures with other men unless she sent more.

Detectives eventually found illegal images of more than 40 other children on Gutierrez’s electronic devices. The federal prosecutor’s office said the case involved “sextortion,” an increasingly common practice among online perpetrators.

“Unfortunately, this type of crime is a growing threat in the Eastern District of Washington and elsewhere,” U.S. Attorney Michael Ormsby said in a news release. “While law enforcement is doing everything it can to stop these predators, it is of the utmost importance parents be vigilant. Any child with access to the internet is vulnerable to these criminals.”

Gutierrez was sentenced about a month after 13 suspected child abusers were arrested in a major sting operation in Spokane County. In that case, detectives from the state’s Missing and Exploited Children Task Force posed as parents on Craigslist and offered to let the suspects have sex with their children.

Those suspects are awaiting trial.