The parents of the 17-year-old who killed a sixth grader and wounded seven others in a shooting at his small-town Iowa high school last week said in a statement Monday that they “had no inkling he intended the horrible violence he was about to inflict.”

Dylan Butler’s parents said in the statement that they are cooperating with investigators as they try “to provide answers to the question of why our son committed this senseless crime.”

“As the minutes and hours have passed since the horrors our son Dylan inflicted on the victims, the Perry School and the community, we have been trying to make sense out of the senseless,” Jack and Erin Butler said in the statement. “We are simply devastated and our grief for the deceased, his family, the wounded and their families is immeasurable.”

Butler took his own life after killing one student and wounding Perry High School’s principal, two other staff members and four other students on the first day of classes after winter break, leaving some with significant injuries. The family of 11-year-old Ahmir Jolliff is planning to hold his funeral Thursday — one week after the shooting happened.

Investigators have said they are reviewing reams of electronic and physical evidence they’ve gathered and are interviewing dozens of witnesses to better understand what happened and why. The Iowa Division of Criminal Investigation, which is taking the lead in this case, didn’t release any updates on the shooting Monday.

Iowa Gov. Kim Reynolds issued a disaster proclamation for Dallas County on Monday to free up state resources for the response to the shooting. Reynolds’ statement indicated the state’s education and health and human services agencies were involved in addition to the Department of Public Safety and its criminal investigation division.

Also on Monday, several hundred students and other protesters marched on the state Capitol in Des Moines about 40 miles away from Perry to push for tighter gun control laws in the state.