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A 19-year-old University of Texas student fired an AK-47 rifle across the Austin campus on the morning of Sept. 28, 2010, then killed himself inside a crowded library as police closed in, authorities said. No one else was seriously hurt.

Police identified the gunman as Colton Tooley, a sophomore mathematics major from the Austin area. Investigators said Tooley boarded a city bus that morning with the rifle hidden in a backpack, the barrel wrapped in cardboard, and got off a few blocks from the Perry-Castaneda Library.

Wearing a dark suit coat and a ski mask, Tooley fired roughly a dozen rounds into the air and into the ground as he walked east on 21st Street, according to a police account. Officers and witnesses said he did not aim the weapon at anyone.

Simultaneous 911 calls reached the Austin and university police departments shortly after 8 a.m. The campus went into lockdown, with text alerts, sirens and loudspeaker announcements ordering students and staff to shelter in place.

Tooley ran into the six-story library, where officers pursued him. A police team found his body on the top floor at about 8:22 a.m., and the medical examiner ruled that he had shot himself. One student sprained an ankle while fleeing, but no one was hit by gunfire, officials said. The all-clear was given around midday.

Investigators never established a motive. Classmates described Tooley as quiet and academically strong. In a report released the following July, university police credited an emergency-alert system installed after the 2007 Virginia Tech shootings with quickly warning the campus, while faulting communication lapses among the agencies that responded.