An Oklahoma man kidnapped his stepdaughter as a child, repeatedly raped and abused her, fathered her nine children and threatened her with violence during the almost 20 years he held her captive, authorities said.

Henri Michelle Piette, 63, was found guilty last Thursday by a federal jury of kidnapping and traveling with intent to engage in a sexual act with a juvenile following a seven-day trial that detailed the horrific conditions Rosalynn McGinnis endured.

McGinnis, now 34, fled with eight of her nine children, in early 2016 after befriending a couple she met at a grocery store in Mexico.

“The victim endured two decades of horrific abuse by the defendant. Her courage led her to escape and rescue her children, and allowed investigators and prosecutors to seek justice on her behalf," U.S. Attorney Brian J. Kuester of the Eastern District of Oklahoma said in a press release. "Ultimately her courage ended the defendant’s reign of terror."

Piette kidnapped McGinnis in 1997 from her hometown of Poteau, Oklahoma, when she was 11 or 12 years old. McGinnis' mother had been in a relationship with Piette, the U.S. Attorney's Office said.

Shortly after kidnapping McGinnis, Piette "took her to a van" and "married" her, according to The Associated Press.

Henri Piette was indicted on charges after allegedly kidnapping his stepdaughter and holding her captive for 19 years. Wagoner County Sheriff's Office via AP

During the almost two decades McGinnis was held captive, she was forced to alter her appearance and use various aliases. In 2000, at the age of 15, she gave birth to Piette's first child, authorities said. She would later give birth to the eight other children fathered by Piette.

When she turned 18, Piette made McGinnis go to a police station in Arizona, where they were living at the time, and tell officers that she ran away from home so she would be removed from the national missing persons registry, she told People magazine in an August 2017 interview. Her name had been added to the list after her mother reported her missing.

“He parked three blocks down the road from the Phoenix Police Department and he had three of my children,” she said. “He told me what to tell them. He said that if I didn’t come back within two hours, I would never see my children again.”

Authorities said Piette avoided being captured by using aliases and moving dozens of times within the United States and Mexico. McGinnis was using the fake name Stephanie when she met Lisa and Ian at the supermarket in Oaxaca, Mexico.

Lisa told NBC affiliate KSHB that she and her husband were in line at the grocery store when they noticed that McGinnis, who was with her children, did not have enough money to pay for her groceries. Lisa and Ian, who did not want their last name disclosed due to fears for their safety, told the outlet that they struck up a conversation with McGinnis and eventually became friends with her and her children.

The couple realized McGinnis needed help when during a visit to see her, Piette accidentally revealed he was 62 years old, Lisa told KSHB. McGinnis was 32 at the time and their oldest child was a teenager, Lisa said.

At some later point, McGinnis, with eight of her children, fled to Lisa and Ian's home after Piette passed out from drinking, according to KSHB. McGinnis' oldest child had already escaped. McGinnis was eventually reunited with her family after getting help from the U.S. Embassy and the National Center for Missing and Exploited Children.

"I'm just so happy that he is put away where he can't hurt anyone anymore," McGinnis told KSHB in an interview last week.

The U.S. Attorney's Office said Piette will be sentenced at a later date. Piette has maintained his innocence and told Fox23 that most of the claims against him are "lies."

"Ninety-nine percent of them are lies. I’m telling the truth,” he told the outlet.

The U.S. Attorney's Office told NBC News that McGinnis and her children, who range in ages from 4 to 19, still "struggle emotionally" from the trauma they endured. McGinnis now lives in Missouri with most of her children, a spokesperson for the office said. The oldest child, a boy, lives on his own.