An Ohio high school student’s class essay about overcoming obstacles ultimately led to a 20-year prison sentence for the man who raped her and her two sisters when they were children.

Anthony Knight, 43, of Fremont, pleaded guilty last week to three counts of felony rape, according to the Fremont News-Messenger. A Sandusky County judge handed down a 20-year sentence and ordered that Knight be registered as a sex offender for the rest of his life.

Ken Arp, a detective sergeant with the Sandusky County Sheriff's Office, praised the courage of the young women for moving forward with charges. They were initially reluctant to do so because they had not reported the abuse when it happened, the News-Messenger reported.

"This happened years ago," Arp told the newspaper in August, when Knight was arrested. "At least it came to light now."

The allegations against Knight first came to light when one of the sisters, a student at Vanguard Tech Center, wrote about overcoming childhood sexual abuse. The News-Messenger reported that staff at Vanguard who read the essay alerted the sheriff's office and child welfare workers, who began an investigation.

Arp said in August that the abuse was addressed by Knight and the victims years ago, but no one reported the crimes to the authorities. Investigators sought charges after the sisters' stories were corroborated by other interviews they conducted, the News-Messenger reported.

NBC News reported that the youngest sister was 7 years old when she was first abused by Knight. All three sisters said they'd been raped, but reported different forms of sex abuse.