Josh Powell had "incestuous" images on his home computer, authorities say

(CBS/AP) SEATTLE - Late Thursday, authorities told the Associated Press a computer in Josh Powell's home two years ago had computer-animated images that depicted "incestuous" sex.

Pierce County Sheriff's Detective Ed Troyer said the images discovered by investigators were realistic, computer-generated depictions of incestuous parent-child relations. The images were disconcerting enough that they prompted a psychologist to recommend last week that Powell undergo an intensive psychosexual evaluation. 

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A lawyer for Powell's in-laws was not invited to see the materials before a custody hearing last week. Attorney Steve Downing said if he has seen them, he might have asked the court to change the terms of Powell's supervised visitation with the boys.

On Sunday, a social worker drove the boys from their maternal grandparents' home to their father's house.

In an interview to air Friday on ABC's "20/20," that worker, Elizabeth Griffin-Hall, said that Powell slammed the door on her after the children were inside the house on Sunday. Hall said she banged on the door and heard Powell tell his son Charlie, "I've got a big surprise for you."

She also heard Braden, Charlie's younger brother, crying. Authorities said Powell used a hatchet on his children then set a house fire that killed them all.

Powell's wife, Susan, vanished in Utah two years ago. Powell had been a person of interest in the case but maintained he had taken his sons on a camping trip the night she disappeared.

Complete Coverage of Susan Powell on Crimesider