A Bucks County man was sentenced Wednesday to 15 years in federal prison for taking sexually explicit photos of pre-teen girls more than a decade ago, according to authorities.

Thomas Rafferty, 68, of Levittown, was charged last year with taking nude photos of three girls between the ages of 6 and 9 at his Philadelphia home from 1999 to about 2004, according to court documents.

In some instances, he photographed one or more of the victims while they were naked and tied to his attic rafters. The images weren't discovered until 2013, when a victim reported her story to authorities.

In August of that year, federal agents searched Rafferty's Levittown home and found 30 of the explicit photos saved on his computer, court documents say.

Authorities also found another 1,000 images Rafferty had created using the photos. Morbid scenes, including a naked child lying down in what appeared to be a crypt and blood pouring out of stab wounds in their chest, were discovered.

Rafferty pleaded guilty in July to one count of coercing a minor into a sexually explicit image, court documents say. The minimum sentence was 10 years in federal prison.

Rafferty's public defender could not be reached for comment.

- Chris Palmer