Police continue to look for a possible motive in the shooting death of Gretchen Crooks, allegedly by her 13-year-old son Noah. Police responding to the Crooks home, in Osage, Iowa, on Saturday night, found the woman shot multiple times after her teenage son - the alleged shooter - called 911. 'We're at a loss. These are good people,' sheriff Curt Younker said. There was no history of domestic abuse or criminal records associated with any Crooks family members. The 13-year-old boy who allegedly shot his 37- year-old mother dead with a hunting rifle is also facing 'unheard of' charges that he tried to sexually abuse her. Now, authorities are saying Noah Crooks also tried to sexually abuse his mother, which mental health professionals say they have never encountered among juveniles Charges filed today in Mitchell County District Court further accuse Noah Crooks, an eighth-grader at Osage Middle School, of assault with attempt to commit sexual abuse against his mother. Shelia Aukes, a licensed social worker in Des Moines who works with young people on a variety of mental health issues told the DesMoines Register: 'The victims in most sex offenses committed by juveniles are siblings, other juveniles or, more rare, other adults. 'A child or adolescent sexually abusing a parent is completely out of the norm, totally unheard of.'