BELLEVUE, Neb. (AP) — Police in eastern Nebraska have arrested a high school student they say threatened to shoot students who participated in a nationwide walkout earlier in the week.

Bellevue police say after arresting the 18-year-old, officers on Friday morning found materials that could be used to make explosives inside the teen’s bedroom.

Police say the student threatened to shoot students at Bellevue West who were participating in a nationwide walkout Wednesday. The walkout was a show of solidarity with survivors of a deadly high school shooting in Florida last week.

Students reported the threats to school officials, and the teen later turned himself in. He has been arrested on suspicion of making terroristic threats, but had not been formally charged by Friday evening.

Bellevue is about 10 miles south of Omaha.