(NEWSER) – Two months after the Sandy Hook school shootings, Justin Carter went on a sarcastic Facebook rant—a rant that could land the 18-year-old in prison for a decade. It's not clear how the conversation started, but an extensive Dallas Observer piece on the case says it was "a duel between dorks" and may have been related to the computer game League of Legends. Carter wrote, in response to earlier comments that are not known, "I'm f---ed in the head alright, I think I'ma SHOOT UP A KINDERGARTEN. AND WATCH THE BLOOD OF THE INNOCENT RAIN DOWN. AND EAT THE BEATING HEART OF ONE OF THEM." A so-far unidentified person in Canada saw the post, alerted authorities, and Carter was arrested at the drapery shop he worked at in San Antonio, Texas. Prosecutors don't have the entire conversation, just the cellphone screenshot containing the above comments sent to them by the Canadian tipster.