The suspect was 20 years old and worked full-time as a Forest County deputy sheriff and part-time as a Crandon police officer, Sheriff Keith Van Cleve said. He would not release the suspect's name but said he was not working at the time of the shooting.
A seventh shooting victim was in critical condition at a hospital in nearby Marshfield, said Police Chief John Dennee. A Crandon police officer who fired back was treated for minor injuries and released.
Gary Bradley, mayor of the city of about 2,000, said earlier Sunday that the suspect had been brought down by a sniper, but Van Cleve would not confirm that officers shot the suspect.
It wasn't immediately clear what the suspect's motive was. The shooting occurred in a white, two-story duplex about a block from downtown Crandon.
One of the dead was 14-year-old Lindsey Stahl, said her mother, Jenny Stahl, 39.
She said her daughter called her Saturday night and asked whether she could sleep over at a friend's house. Jenny Stahl agreed.
"I'm waiting for somebody to wake me up right now. This is a bad, bad dream," the weeping mother said. "All I heard it was a jealous boyfriend and he went berserk. He took them all out."
The State Patrol and the Crandon Fire Department detoured a steady stream of traffic from two blocks of U.S. Highway 8 in the downtown area. Some residents stood in nearby front yards.
This is tragic and the tragedy is always magnified in a town of this size, but the town, from reports so far, seems to be pulling together to deal with it.
Our thoughts and prayers go out to the critically injured patient and to the families of those killed as well as the town itself.