He made the threats because he was unprepared for class.
The alert was issued just before 1:30 p.m. Thursday.
The man and his wife were going through a divorce, and he was upset she was dating other men.
The evacuation was ordered around 4 p.m. Monday.
Police say the credibility of the threat is undetermined.
Parents have been told not to come to the school.
The 20-year-old from Blaine is facing federal charges.
Authorities say the 51-year-old made the threat during a phone call to the center on Friday.
The bomb threat was called in Tuesday afternoon.
All students and non-essential staff have been sent home.
Threatening emails were sent to businesses in Waite Park, among others.
The restaurant was 75 percent full, BMTN is told.
They've had closed down an entrance to the parking lot.
The school is being searched by bomb dogs.