One day after a Westbury teen was arrested and charged with making a terrorist threat, officials at Westbury Middle School said a lockdown has been lifted -- and classes are back to normal Tuesday.

The school had gone into lockdown mode on Monday after word of the threats, posted on Facebook, were made public. Tensions were already running high at schools across the country, after Friday's elementary school massacre that left 20 first-graders and six adults dead in Newtown, Conn.

Nassau County police said the 13-year-old Westbury boy was arrested Monday, saying he used a computer to send threatening messages to two 13-year-old girls that he felt were bullying him.

The boy logged on to a friend's Facebook account and sent the messages between Dec. 14 and Dec. 15, police said. Detectives traced the messages to the teenager, police said, and he was arrested at his home.

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The boy, whose name was not released because of his age, was to be arraigned Tuesday in Family Court in Mineola.

With Bill Mason