A sheriff's deputy shot and killed six people in the northern Wisconsin town of Crandon before he was shot dead.
Five of the victims ranged in age from 14 to 20, and another victim was in critical condition, the Milwaukee Journal Sentinelreported.
Tyler Peterson (20), who was accused of storming into his ex-girlfriend's house, was shot by the police, the newspaper said. Peterson's former long-time girlfriend was among the dead.
Peterson was a part-time police officer in Crandon, a town of about 2,000 people about 290 kilometres north of Milwaukee.