PORTLAND, Ore. (AP) - A Beaverton man was sentenced Monday to more than 24 years in federal prison after posing online as a teenage boy dying of leukemia to coerce young girls into sending him sexually explicit images.

Joshua Kistler, 31, chatted regularly with at least nine girls across the country who ranged in age from 12 to 14. He used the condition to gain the girls' sympathy, according to the U.S. Department of Justice.

He did send them pictures of his stepson, an actual 15-year old, to further his story, authorities said.

Several victims said they loved and trusted Kistler, who asked them to send photos of them nude or perform sexually explicit acts for him in front of Web cams.

The victim whose case led to Kistler's arrest was a Utah girl who started chatting online with him when she was 12.

According to the U.S. Department of Justice, Kistler told he victim he had cut off contact with another girl because of the victim's jealousy and that the other girl had killed herself. Overcome with guilt, the Utah girl attempted suicide, which drew the involvement of law enforcement.

The girl attempted suicide a second time after the mother tried to stop the relationship.

Kistler also posed as the stepfather of his online character. In one case, a victim and her mother visited the "stepfather" during a family trip, believing the teenage boy was away receiving treatment.

The court will decide later if Kistler owes his victims money for restitution.

Kistler told agents that he knew what he was doing was wrong and that he'd always "been a collector."

Kistler, who pleaded guilty to charges of producing child pornography, apologized during his appearance before U.S. District Judge Ancer Haggerty.

"I'm sorry for the harm I've caused," he said. "I wasn't aware I was causing any harm."

According to court documents, Kistler had computers that contained files of movies of young women, some taken without their knowledge. He also had thousands of images of child pornography. 

(Copyright 2007 by The Associated Press. All Rights Reserved.)