BRANSON, Mo. (AP) — A Missouri high school student faces a felony charge after authorities say he posted on social media that he was going to buy an assault rifle and “make history.”

William James Nelson, an 18-year-old from Branson, was charged Thursday with making a terroristic threat, the Springfield News-Leader reported. No attorney was listed for him in online court records.

Branson police were tipped off before midnight Tuesday about a series of SnapChat messages that a female classmate received. Officer Joseph Edwards wrote in charging documents that Nelson admitted during an interview Wednesday that he had sent the messages in which he pledged “allegiance to Allah,” asked where he could buy a gun, discussed needing a bulletproof vest and talked about letting out “all the anger and hurt.” He told the classmate that if she hears his name on the news, she will know why, authorities allege.

SnapChat messages are automatically deleted after they’ve been viewed, but the classmate took screen shots of them and provided them to police.

Edwards wrote that Nelson told him that he was off his medication and was scheduled to meet soon with a mental health care provider, and that he planned to show up at Branson High School at lunchtime on Dec. 14 with a gun.

“He stated he was going to go in to the lunch area with the AR-15 and commit suicide so everybody could see how much they had hurt him,” the officer wrote in a probable cause statement. “When asked if he was going to harm anybody else, William James Nelson told me he did not plan to do but (thought) about maybe hurting some people.”

According to court documents, Nelson told the officer he planned to leave a note in his bedroom, presumably for family to find, stating his plans. Nelson also told police Wednesday that he planned to meet an unnamed individual that day to buy an AR-15 assault rifle.

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Information from: Springfield News-Leader, http://www.news-leader.com