The social worker who witnessed the explosion at Josh Powell's home on Sunday, said he had a sheepish look and that he told his sons that he had a surprise for them. Utah police also reportedly found incestuous sex images on Powell's computer in his home two years ago and had forwarded the documents to Washington state authorities, according to reports.

Pierce County Sheriff's Detective Ed Troyer told The Associated Press on Thursday, that the images investigators found on Powell's home computer in Utah were realistic computer-generated portrayals of incestuous parent-child relations.

It's family-oriented in nature, Troyer said. It is incestuous.

The two boys - Braden, 5, and Charles, 7 - were on a supervised visit with their father when they were blown up in an explosion at Powell's home on Sunday. Josh Powell lost custody of the boys last year and his children were placed into the custody of their mother Susan's parents Chuck and Judy Cox. This was because Powell's father, Steven, was arrested last year, on charges of 14 counts of voyeurism and one count of possessing child pornography.

Powell tried to regain the custody of his boys but was told by a judge last week that he must undergo a psycho-sexual evaluation.

In-Laws Lawyer Never Saw Images

The AP reported that authorities have said the images found in Powell's home two years ago were enough to prompt a psychologist to recommend that he undergo intensive psycho-sexual evaluation.

Steve Downing, a lawyer for Powell's in-laws, told The AP that he hadn't seen the materials prior to the custody hearing and had he seen the images he might have asked that the court changed the terms of the supervised release.

Downing told the news organization that he didn't know he was allowed to see the images until Thursday, days after the explosion at Powell's house. Powell killed himself and the two boys after attacking them with a hatchet.

That would have absolutely given me the opportunity to submit a declaration about our deep concern, Downing told The AP. I was approved ... to view those pictures and I was never notified. I could have gone into all the reasons why the visitation could have or should have been restricted.

Downing said he might have asked for Powell's visit to be in a public palace.

Powell Had a 'Sheepish' Look

Elizabeth Griffin-Hall, the social worker who took the boys for the supervised visit on Sunday, told ABC News that she heard Powell telling Charlie, I've got a big surprise for you. Then she said she heard Braden cry out. It was then Griffin-Hall began knocking at the door and yelling to be let in.

I saw Josh for just one second. His eyes caught mine. He had a look in his eyes that was just kind of sheepish and then he slammed the door, Griffin-Hall told ABC.

She smelled gasoline and called 911, but was told they had to respond to emergencies, life-threatening situations first.

Well this could be life-threatening, a fearful Griffin-Hall is heard on audio tape telling the 911 dispatcher. She told them she could smell the gas. Soon Griffin-Hall was knocked away by a huge explosion.

Josh Powell was really, really evil, Griffin-Hall told ABC. I never saw any suicidal indicator from him. He didn't look like a monster. He didn't look like somebody that was going to kill his children.

Powell was a person of interest in the case of his missing wife Susan who disappeared from their Utah home in 2009.