The former stepfather of a 12-year-old girl who was kidnapped and slain in Vermont last year has pleaded guilty to transportation of child pornography.

The plea by Raymond Gagnon was accepted by U.S. District Judge Xavier Rodriguez in San Antonio on Monday. Gagnon faces from five to 20 years in prison when he is sentenced in July.

Authorities had searched Gagnon's home in Texas after his former stepdaughter, Brooke Bennett, disappeared in Vermont last summer. She was found dead a week later. Authorities say she had been drugged and raped.

Her uncle, Michael Jacques, a convicted sex offender, has been charged in the killing. Police said Jacques had called Gagnon several times when the girl was first reported missing.

Gagnon was initially charged with obstruction of justice in Brooke's disappearance and death but federal authorities later dropped the count.

He has lived in San Antonio since 2007, but police in Vermont said he traveled there frequently.

In the plea agreement, Gagnon admitted to having hundreds of images and video files of prepubescent children engaged in sexually explicit conduct, including sexual acts with adults. Gagnon collected many of the images when he was living in Alabama, before moving to Texas, according to the document.

He faces additional charges of possession of child pornography in Alabama, where he lived before moving to Texas. Monday's plea agreement does not affect those charges.

Gagnon had married Brooke's mother, Cassandra, in 2000, after they moved from Vermont to Alabama. The couple separated in 2004, and Brooke, her sister and mother returned to Vermont. Raymond and Cassandra Gagnon divorced in 2006.