The UT campus was on lockdown for nearly four hours Tuesday because of a shooting incident that ended when the gunman, armed with an AK-47 rifle, took his own life after unleashing a barrage of bullets and being cornered by police on the sixth floor of the Perry-Castañeda Library.

Campus administrators identified the gunman as 19-year-old mathematics sophomore Colton Tooley.

A half-dozen law enforcement agencies, including the Austin Police Department, University of Texas Police Department, the Texas Department of Public Safety and the Austin Independent School District Police Department, responded to the shooting and its aftermath.

Officials said no students were hurt in the shooting, although a couple of students were mildly injured during the evacuation process.

“I am grateful to our campus community for the way it responded to the emergency that took place at the Perry-Castañeda Library [Tuesday] morning,” UT President William Powers Jr. said in a statement issued Tuesday afternoon. “I extend my sympathy to the family, friends and classmates of the young student who took his life.”

The lockdown was lifted at 12:15 p.m. The University was then closed and nonessential personnel were released for the remainder of Tuesday. UT shuttles routes ran, but only in the outbound direction so students and staff could get home, said UT spokeswoman Rhonda Weldon.

The incident began just after 8 a.m. as Tooley walked from 21st Street near Guadalupe Street, heading deeper into campus wearing a dark suit, ski mask and carrying an AK-47 in his hand.

The University sent the first emergency text messages warning of an armed man on campus at 8:23 a.m. The message was quickly followed by a warning from UT officials for students and staff to find shelter and lock all doors.

“He had a black mask and he was walking down the street,” said Ruben Cordoba, a maintenance worker at Dobie Center who was working on the plaza level of the dormitory, which is three stories above 21st Street. “I thought he was joking because he had an AK-47 in his hand … I heard three shots to the left and three shots to the right.”

Other eyewitnesses said they heard as many as 10 shots, and said they thought he was shooting at the University Catholic Church and the South Mall. After shooting, he continued to run toward the PCL.

Lawrence Peart, an international relations junior, was locking up his bike at the library when he heard the first gun shots. He said a taxi came down the street honking its horn to warn the students, but he didn’t think much of it until he saw students running.

“So I start advancing toward the entrance and a man — pretty tall in a black business suit, ski mask and an AK-47 — runs in front of me, so I froze,” Peart said. “He was running down the 21st Street along that brick wall that’s beside the PCL and he glances over at me. He looked at me in the eyes then waved his arm as if to say, ‘Don’t come in here. Go away.’”

Officers chased Tooley off the street and into the library, said Austin Police Chief Art Acevedo. Once inside, Tooley ran to the stairwell and climbed the stairs to the sixth floor, where he took his own life at 8:50 a.m., Acevedo said.

“Almost immediately, members of [APD] and [UTPD] ended up on campus, spotted the suspect and gave chase to that suspect,” Acevedo said. “I want to commend the students of the University of Texas that led the way to the suspect — that as our officers ran and tried to find and chase after him, the students kept pointing [the officers] in the right direction.”

Authorities held a press conference on the UT shooting at the AT&T Executive Education and Conference Center.

In the immediate aftermath of the shooting, tactical response teams from APD and DPS searched surrounding buildings for a rumored second suspect. However, officials ruled out any such possibility and said that reports of a second suspect resulted from conflicting descriptions of the shooter.

UTPD Chief Robert Dahlstrom and Acevedo credited joint exercises between both agencies for the quick response and lack of fatalities.

“There’s no doubt that the training paid off in this situation and prevented a much more tragic situation than what we had happen this morning,” Dahlstrom said.

— Additional reporting by Gerald Rich