The reference to the threatening phone messages and completed calls is contained in a search warrant affidavit. Westmoreland County District Attorney John Peck said neither student was among the victims in Wednesday's attack at Franklin Regional High School.
County detectives got the warrant for the home of Alex Hribal. He is charged as an adult with four counts of attempted homicide and 21 counts of aggravated assault.
Hribal's attorney and the district attorney did not return messages seeking comment.
Four students are still hospitalized, three in critical condition. The fourth was upgraded to fair condition Monday.
Teachers returned to the school Monday but classes don't resume until Wednesday.