Police were already keeping an eye on 17-year-old expelled student Jared Cano when they were tipped off that he was allegedly planning to bomb his old high school when classes resumed. In his apartment, they found shrapnel, plastic tubing, timing and fuse devices that he was amassing in a plot he intended to be worse than the Columbine mass killings, police said Wednesday.

Before Tuesday's discovery, Cano has been arrested several times, most recently accused of breaking into a house and stealing a handgun, Tampa police said. He had a court-ordered curfew and was on a police watch list. Officers checked up on him from time to time.