Five teenage boys accused of plotting a shooting rampage at their high school on the anniversary of the Columbine massacre were arrested Thursday after a message authorities said warned of a gun attack appeared on the Web site MySpace.com.

Sheriff’s deputies found guns, ammunition, knives and coded messages in the bedroom of one suspect, Sheriff Steve Norman said. Authorities also found documents about firearms and references to Armageddon in two suspects’ school lockers.

“What the resounding theme is: They were actually going to do this,” Norman said.