Authorities in Wisconsin have made an arrest in the shooting of three young swimmers.

The arrest Friday ended a dragnet that included more than 100 law enforcement officers around the northern Wisconsin town of Niagara. Few details on the arrest, including the suspect’s identity, were immediately released.

Marinette County Sheriff Jim Kanikula says nine young adults had gathered near a railroad bridge on the Menominee River when the gunman came out of the woods and opened fire Thursday with a military-style assault rifle.