Authorities say a 12-year-old boy brought a knife to a Bakersfield middle school with a plan to take his class hostage, carry out a sexual assault and then kill himself. Kern County Sheriff´s officials say the alleged plot was foiled on Thursday when another student alerted a teacher, who called a security guard. Sheriff´s Commander Marty Williamson says the boy came to Sierra Middle School with materials in his backpack to carry out his plan. In the backpack authorities say the security guard found handcuffs, condoms, an undisclosed sexual device, a bottle of beer and food. The 12-year-old was held at juvenile hall on charges of possession of a weapon and making terrorist threats.