NIAGARA, Wis. -- A Marinette County official said that the massive search for a camouflaged gunman who fatally shot three people and injured one other along the Menominee River is over.

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Authorities arrested Scott J. Johnson, 38, of Iron Mountain, Mich., Friday morning in the area where the victims were shot Thursday.

Marinette County officials said Johnson is expected in court Monday or Tuesday and that it was unclear whether charges will be filed against Johnson before his first court appearance.

Chief Deputy Jerry Sauve said Johnson complied with officers' orders to throw down his assault rifle as they arrested him in a wooded area in the Town of Niagara. Sauve said Johnson was also carrying a knife. He has not been charged in the case.

"We would like the community to know up here that we are quite confident we have who we are looking for the actor in this matter and that people are being allowed to return to their residences," said Sauve.

Johnson allegedly shot and killed three Michigan teenagers and wounded a 20-year-old Michigan man Thursday evening as a group of young people gathered to go swimming near the Wisconsin-Michigan border near Niagara.

More than 100 law enforcement officers from at least 10 local and state agencies had searched the area for the gunman.

Marinette County Sheriff Jim Kanikula said nine young adults, five from Michigan and four from Wisconsin, had gathered near a train bridge on the Menominee River Thursday evening when the gunman came out of the woods and shot the four.

Tiffany Pohlson, 17, Anthony Spigarelli, 18, and Bryan Mort, 19, were killed. Daniel Louis Gordon, 20, was wounded. All were from Michigan.

"Unbelievable, just devastating," said Cathy Dallnpiazza, who was evacuated from her home because of the shooting. "I don't even have any words to describe it."

Two of the bodies had not been removed from the scene by Friday morning because officials feared the shooter was still in the area.

"We're bound to know who these people are and it's just terribly sad," said Lyla Nenning who was also evacuated from her home.

Roadblocks were set up in the area and some homes were evacuated as authorities searched for the gunman.

A 24-year-old woman has alleged that Johnson sexually assaulted her at the same site the day before. Authorities said they're not sure whether the allegations are related to the shooting.