The parents of a teenager who killed four people in a school shooting in Michigan last year say they didn’t have any reason to think their son had mental health issues, according to a court filing cited by the Detroit Free Press. Ethan Crumbley pleaded guilty in October to the attack at Oxford High School that he carried out at age 15. His parents, Jennifer and James Crumbley, are charged with involuntary manslaughter—prosecutors say they ignored Ethan’s mental health problems, failed to get him help, and instead bought him the gun he used to carry out the shooting. “The Crumbleys maintain that they did not have any reason to believe that the shooter had mental health concerns that would necessitate mental health treatment,” the parents’ defense lawyers wrote in the new filing. The document said the pair, whose trial is scheduled for January, admit that Ethan was “experiencing sadness” over the loss of his grandmother, dog, and a friend who moved away. “However, the evidence claiming that the shooter was asking his parents to get him to a doctor or get him help was sent in text messages to the shooter’s friend,” the filing continues. “This was not information that either parent knew he was claiming.”