An image shared on Snapchat warned of the "best school shooting yet."
The synagogue and its preschool have closed Friday.
He admitted to leaving the voicemail to cause "political pain."
"We have no reason to believe there was a threat to the school," the principal said.
Charles Sauke, 22, pleaded guilty to possession of an unregistered firearm in federal court.
The threat was determined not to be credible.
The alert was sparked in northwestern Wisconsin.
"I want you to be as scared as possible," the voicemail allegedly says.
The utility workers were on the site of a cell phone tower.
She told police silently she needed help when she answered the door.
iHeartMedia radio stations are located at the Towers at West End.
The 36-year-old white man was arrested on June 19.
Four schools won't re-open until Monday.
The candidate has denied the letter, saying his campaign manager wrote it.
She says giving him a stern sentence will just fuel his anger and resentment.
The mayor has been forced to increase security in the wake of the threats.
Superior Mayor Jim Paine made the announcement Tuesday morning.
The school says police addressed the matter with the student.
It was homecoming weekend for Simley High School.
A 19-year-old man is being held on terroristic threats, assault and public nuisance charges.
The man worked for Minneapolis Public Water Works Treatment and Distribution Service.
The 40-year-old became enraged on the first day of classes.
The racist death threat comes after she once again hit national headlines.
The girl allegedly threatened to "shoot up" the southern Minnesota high school.