The Ezra Baker School student openly admitted to his teacher he brought the grenade into class in his backpack Wednesday, WCVB-TV, Boston, reported. The teacher reportedly told the school principal, who then notified authorities.

Some 400 children were removed from the school after the grenade was located. Authorities said the 8-year-old was carrying an inert device from World War II.

Dennis police took possession of the grenade and gave it to state officials for disposal, WCVB reported.

Letters were sent home to parents, advising them to look into their children's backpacks in the morning.