Grand Chute Police identified the suspect as Alexander Kraus, 17. Police said they are his grandparents.
The 17-year-old told investigators that he fatally shot the elderly couple and was planning to cause harm at his high school in eastern Wisconsin, police said Monday.
Police officers responding to a 911 call for assistance found the bodies of the man and woman, identified by Grand Chute Police as 74-year-old Dennis Kraus and 73-year-old Letha Kraus, at their home in Grand Chute about 11:30 a.m. Sunday, April 14, Officer Travis Waas said.
Kraus was being held in the Outagamie County Jail and was not immediately charged. Police said in a news release that he could be charged as an adult with two counts of first-degree intentional homicide.