Antigo - An 18-year-old gunman opened fire outside of a high school prom in northern Wisconsin, wounding two students before a police officer who was in the parking lot fatally shot him, authorities said on Sunday.The attack happened late on Saturday outside the Antigo High School prom, said Eric Roller, the chief of police in Antigo, a community of about 8 000 people roughly 200km north of Milwaukee.Roller told reporters that the gunman shot the two students as they exited the building, though he didn't say if investigators believe they were specifically targeted or discuss a possible motive for the attack."Officers were in the parking lot patrolling the activities and heard the shots and an officer immediately fired upon the shooter, stopping the threat," he said. He said the gunman was then taken into custody.Authorities said the two students and the attacker were taken to a hospital and that investigators don't believe there is a further threat to the community.Langlade County Coroner Larry Shadick told The Associated Press that the attacker died shortly after 01:00 in the intensive care unit of a Wausau hospital. He said further details would have to come from police.Authorities haven't disclosed the identities of the wounded students or the attacker, but he said the victims' families had been contacted. Roller didn't respond to repeated requests for further information.After the attack, students were escorted from the prom to safety and the victims' families were notified.