Police identified the student as Marcus Wheeler.
"After the incident, the lockdown remained in place to allow investigators to keep the scene secure," Tempe police spokeswoman Molly Enright says in a statement. "There was no apparent threat to other students or staff, and this was an isolated incident."
Police say that around 8:50 a.m. today, school staff members reported to the school's dedicated police officer that there was someone on the campus with a gun.
The police officer tried to talk Wheeler into putting down the gun, but Wheeler shot himself.
Wheeler actually posted on Twitter this morning that there was "going to be a suicide in the school."
there is going to be a suicide in the school right now— TIGERHOODS?? (@marcuswheeler69) May 12, 2015
Wheeler, who previously had attended Chandler's Hamilton High School, was a cross country state champion in 2014.
The school was locked down until roughly 10:15 a.m., when students were allowed to go home, police say.
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