Joseph J. Ostrowski, 29-year-old former Pennsylvania high school football coach, has been sentenced to 25 years in federal prison Friday, for cyber-stalking Michigan State University students.

According to the records, Ostrowski used Facebook accounts of others to trick their friends into engaging in sexually explicit acts on Skype accounts.

Michigan FBI and the Michigan State University Police Department began investigating the case in 2011 after Michigan State University police were informed that the university students' social-networking sites had been hacked and were being used to annoy, blackmail and frighten students.

"Specifically, having accessed the 'Facebook' accounts of other persons without authority, taken them over, and blocked the true account holders from regaining access to those accounts, (Ostrowski) used those accounts to contact persons in East Lansing and, posing as the true account holders, persuaded and tricked persons in East Lansing into engaging in sexually explicit acts over their 'Skype' accounts,' which defendant recorded without their knowledge," Assistant U.S. Attorney Hagen Frank said.

U.S. District Judge Edwin Kosik instructed Ostrowski to be on supervised release for life once his imprisonment ends.

Ostrowski influenced others to provide naked photos or videos of themselves and demanded additional images from certain victims by threatening to disclose the photos or videos to others. He either kept the images with himself or shared some of them.

Mostly, the victims were athletes known to Ostrowski. Sometimes Ostrowski posed as an older student or alumnus and convinced victims that the photos or videos were part of a hazing ritual.

He is alleged to have provided some nude photos to others, including schools, employers and friends of the victims.

During the probe, police personnel discovered that Ostrowski's crimes, which started in 2006, were not confined to only Michigan state, but he had approached both minors and adults in Pennsylvania, New York, North Carolina, California, Texas, Florida, New Jersey, Ohio, Virginia, Minnesota, Indiana, Alabama and Maryland.

He was a football coach at Holy Redeemer High School for a year until his arrest, May 2012.