A Louisiana man who convinced multiple girls – including one from West Michigan - to send him nude photos and then used the images for blackmail, was sentenced Friday to 20 years in prison.

The ‘sextortion’ case involving Matthew Chaney Walker targeted at least 45 girls in the U.S. and Canada, including an 11-year-old Ottawa County girl.

Presenting himself as a tween, Walker used the social application Kik Messenger to make contact with his victims. He offered "flirtation and flattery'' to reassure the girls, according to a federal indictment. Some girls were only eight years old.

Walker, 26, was arrested in March, 2015. He pleaded guilty in January to 10 felony counts, including production of child pornography, which carries a mandatory minimum term of 15 years in prison.

Walker appeared for sentencing in U.S. District Court in Baton Rouge. In addition to prison, Chief U.S. District Court Judge Brian A. Jackson slapped him with a $100,000 fine and a $6,247 bill for restitution.

"This case provides another tragic cautionary tale for anyone concerned about the dangers posed to our children by criminals on the Internet,'' Baton Rouge U.S. Attorney Walt Green said in a Dec. 2 statement. "Today's sentence appropriately reflects the seriousness of these crimes and the need to deter others inclined to engage in similar activity.''

In one instance, Walker messaged a crying 11-year-old from Ontario: "You've been tricked. I'm a guy. Do u really want to be known as a whore at school?'' federal court documents show.

Police arrested Walker after receiving several complaints from parents. Walker was indicted on myriad charges, including extortion and production of child pornography. Although multiple victims were identified, federal prosecutors charged him in four cases, including the one from Ottawa County.

The case involving the Ottawa County girl started in March, 2015; he broached the topic of trading nude pictures with a caveat: "This has to be secret,'' court documents show.

Walker eventually determined where she lived and the name of her school. What started as flirtation became increasingly menacing, with Walker demanding she send graphic images of herself on a bed and in front of a mirror. "Hey, I sorta feel uncomfortable sending pics of myself,'' the Crockery Township girl messaged Walker, according to the indictment.

"You've been tricked,'' he responded. "We have your nudes with your face and your school email and information. We will email the school your nude pic and your parents and family and friends and school will all see. You'll be expelled.''

Walker then upped the online ante: "There's only one way out of this: you must obey us completely and do whatever we say to do. Obey us, and when we're done, all the pictures will be deleted and we won't email your school. What's your choice?''

"Please stop. I'll obey,'' she responded.

There was no "we," of course. Walker acted alone. Similar scenarios played out in multiple states and in Canada over the span of eight months.

The anonymous nature of the online relationship allowed Walker to misrepresent his name, age, gender and interests, federal prosecutors said. Pretending to be a teenage girl, Walker used different online identities and screen names to communicate with his victims. Each victim eventually told a family member who intervened and contacted police.