DARLINGTON, Wis. (AP) -- A Waukesha man accused of killing three retired Wiota farmers is changing his plea to not guilty by reason of mental disease or defect. The Wisconsin State Journal reports 31-year-old Jaren Kuester changed his plea Monday after a judge ruled he was mentally competent to stand trial. A trial has been tentatively set for October. Kuester faces three counts of first-degree intentional homicide. Police say he used a fireplace poker to kill 70-year-old Gary Thoreson; his wife, 66-year-old Chloe Thoreson; and his brother, 76-year-old Dean Thoreson in April. An insanity defense will deal with Kuester's state of mind at the time of the alleged killings. Kuester's father, Jim Kuester, says that before the killings, he told Waukesha County authorities his son was dangerous and needed hospitalization.