WASECA — Three more people were charged Friday in what investigators say was a teen’s foiled plot to kill his family and students at his southern Minnesota high school.

Michael Steven Jacobs, 40, of Waseca, is charged with illegally selling a handgun to the 17-year-old boy who’s accused of plotting to kill his family and students at Waseca Junior and Senior High School.

Two 17-year-olds are charged in juvenile court of helping the accused teen make explosives, reports said. The juvenile petitions say the two boys were unaware of the teen’s plans for the explosives.

The teen was arrested in April after authorities said they found him in a storage locker with bomb-making materials. Authorities said they also found guns, explosives and a 180-page journal that outlined a plan to kill his family, set a fire to divert first responders, then go to the school and “kill as many students as he could,” according to court documents.

Police found a .45 caliber handgun while searching the boy’s bedroom on April 29, according to the complaint against Jacobs. Authorities learned Jacobs sold the pistol to the boy because he said he needed money, the complaint said.

Jacobs told investigators that the teen said his father wanted to buy the pistol, but the father told police he did not know his son was buying a pistol until the boy came home with it, the complaint said.

The complaint said Jacobs sold the gun and a magazine to the teen. for $350 Jacobs never told police about the pistol sale as required by law, the complaint alleges.

Police said Friday their investigation continues to indicate that the teen accused of plotting the attack was the only person with information about the alleged plot.

A hearing on whether the teen should be certified to stand trial as an adult is set for July 30.

The other two teens are scheduled to appear in juvenile court July 7 and Jacobs in Waseca County District Court on July 8.