KINSGFORD, Mich. -- A 17-year-old said that a man accused of randomly killing three teens along the Menominee River regularly swam there.

Lenny Poquette told the Milwaukee Journal Sentinel that he had planned to come to the swimming spot to meet his friend Bryan Mort the afternoon of the shootings -- Thursday -- but his boat was out of gas.

Mort and two other Michigan teens were shot to death; another teen was wounded.

Police allege that on Thursday afternoon, Scott J. Johnson, 38, of Iron Mountain, Mich., emerged from a bush dressed in camouflage and opened fire on the teens as they relaxed along the Menominee River between the Wisconsin and Michigan borders.

Authorities said Johnson disappeared for nearly 16 hours after the shooting before emerging from a wooded area, throwing down his rifle and surrendering to police.

Poquette said Johnson always swam in the area alone and spoke very little. He said he last saw Johnson at the spot about 10 days ago. He said he seemed cool but also thought he was "messed up."

Two 14-year-old boys said Johnson was a regular at the swimming hangout. They said Johnson would arrive alone and avoid most people but occasionally chat with them and a few other teens. Conrad LaPointe, who lives in Johnson's neighborhood in Kingsford, Mich., said Johnson was always nice to him, but when girls were swimming he would stare at them.

Johnson is expected to make a court appearance early next week. Marinette County authorities said Johnson has been well-behaved in jail as he awaits his first court appearance.

Marinette County Chief Deputy Jerry Sauve said Johnson is under "extra monitoring" but has done nothing in custody to warrant a suicide watch. Police said Johnson has complied with authorities ever since a 16-hour manhunt for him ended Friday morning.

Marinette County District Attorney Brent DeBord is expected to file charges in the shooting as early as Monday.

Attempts to contact Johnson or a representative have been unsuccessful. Officials in Marinette County, Wis., said they didn't know whether Johnson had an attorney.

Investigators have not determined a motive in the shooting.

A 24-year-old woman has alleged that Johnson sexually assaulted her at the same site the day before. Johnson hasn't been charged in the case. Authorities said they're not sure whether it's related.

Two towns united in sorrow Saturday after the slayings that took place at the body of water that has always divided them.

Mourners in Niagara, Wis., and Kingsford, Mich., scrawled "rest in peace" in crayon on signs in car windows and hung posters in store windows urging residents to "pray for the families."