A sword-wielding teenager killed his mother and injured three others before police shot and killed him.
When officers arrived at the family's home Friday, they saw 16-year-old Josh Gilchrist wielding a long sword one officer described as "something you'd probably see in an ancient knight-type movie."
Gilchrist struck one of the officers several times before the others fired shots and killed him, Huron Police Chief Doug Schmitt said Friday.
"We don't have any background or any events leading up to the assault this morning that would give any indication of a motive," Schmitt said.
Police found 49-year-old Betty Gilchrist dead. Fourteen-year-old Rebekah Gilchrist and a foreign exchange student were injured. The injured officer was treated at a local hospital and released, the AP reports.
Four officers were placed on administrative leave pending an investigation, which is standard procedure when police fire a gun.
The choice of the city of Helsinki is not incidental as the capital of Finland had hosted US-Soviet negotiations on the limitation of nuclear stockpiles in 1969