Ft Worth, TX  –  A Fort Worth sex offender who videotaped himself sexually molesting a 6-year-old girl he lived with was sentenced Tuesday to 40 years in federal prison, the U.S. attorney’s office said.

Mark Anthony Pape, 24, had pleaded guilty in October 2014 to one count of production of child pornography and one count of committing the offense as a registered sex offender.

Pape was convicted as a juvenile in 2006 of indecency with a child for molesting his adopted sister, who was 4 at the time.

He has been in federal custody since his arrest last year in San Marcos.

In one of the videos, Pape assaulted the victim at his father’s home in February 2014, federal authorities said.

When Pape uploaded child pornography to the Internet, Google alerted the National Center for Missing and Exploited Children, according to a criminal complaint.

The center forwarded the information to police, who searched his mobile home and seized Pape’s cell phone and computer equipment.  Police found photos and videos of Pape sexually assaulting the victim as well as more than 100 images of her, prosecutors said.

They also found other child pornography on his devices, court records show.

When confronted with the evidence, Pape initially told police he was trading in child pornography to “catch other predators,” according to prosecutors.

He later confessed to molesting the victim since moving into his father’s home on Churchill Road in June 2013, authorities said.  He said he videotaped the molestation and took sexually explicit photos of the victim, reports show.

While in custody, Pape told other inmates that he molested other young girls in his neighborhood, prosecutors said.  Fort Worth police have investigated similar allegations, according to prosecutors.