AUSTIN -- A ski-masked student armed with an AK-47 spread terror at the University of Texas at Austin on Tuesday as he fired randomly into the air before running into a library, where he killed himself, investigators said.
No one else was injured in the hours-long drama, and UT officials praised the swift response from a combined force of UT and Austin police.
The Travis County medical examiner identified the gunman as 19-year-old Colton Tooley, a sophomore mathematics major from Austin.
Late Tuesday, authorities still had not determined a motive.
Tooley lived with his parents in a tranquil middle-class neighborhood in Austin and was described by neighbors and former teachers as an amicable teenager with a standout scholastic record in high school.
The drama immediately brought back memories of August 1966, when Charles Whitman climbed to the observation deck of the UT Tower and began shooting. Fourteen people died, and 31 were wounded. Whitman had also killed his wife and mother the night before.
Shots in the air
On Tuesday, the first shots were fired about 7:50 a.m. as the black-clad gunman walked through part of the campus, alternately shooting into the air and at the ground as horrified students and faculty members ran for safety. Some witnesses said the gunman waved and smiled.
UT Police Chief Robert Dahlstrom said that when the gunman saw police officers approaching, he rushed into the Perry-Castaneda Library and made his way to the sixth floor, where he killed himself.
About 100 students were reportedly in the library and immediately responded to shouts from library officials to evacuate the building.
Authorities locked down the sprawling university -- nicknamed "the Forty Acres" -- until early afternoon as investigators and SWAT officers swarmed the campus searching for a possible second gunman and for explosives. Helicopters and armored vehicles were also dispatched. Emergency sirens blared throughout the morning.
"It was a good response," Dahlstrom said. "We're very fortunate that no one else was injured other than the lone gunman."
At a late-morning news conference, UT President Bill Powers said that police had secured a perimeter and that there were no other reports of injuries.
Fears of a second gunman emerged because of conflicting descriptions of the shooter, Dahlstrom told reporters. But authorities later said they had concluded that the gunman had acted alone.
A semblance of normalcy returned to the campus by late afternoon, but classes did not resume.
Seeking a motive
Police, meanwhile, went to Tooley's home to interview his family and search for clues to explain the bizarre episode.
Tooley graduated from Crockett High School in 2009, where he was "an excellent student who excelled in every subject and was ranked seventh in his class," Crockett Principal Craig Shapiro said in a statement. "His teachers recall him with words such as 'brilliant,' 'meticulous and 'respectful.'"
"All of us in the Crockett High School community are shocked and saddened by today's tragedy at the University of Texas," Shapiro said. "Our hearts go out to the family and friends of Colton Tooley."
Neighbors described Tooley and his parents as a quiet but pleasant family who typically kept to themselves.
"I just want to express my condolences to the family," Bryan Winkle said.
Winkle said that he and his family moved into the neighborhood nine years ago and that the Tooley family was there when they arrived. "They were a very quiet family," he said. "Colton seemed like a very quiet young man as well."
'We're very fortunate'
Austin Police Chief Art Acevedo confirmed reports that the gunman killed himself and said no shots were fired by law enforcement officers. He credited students and faculty members for cooperating with officers to maintain order.
"The students did their part," Acevedo said. "They cleared the streets and the grounds in a very quick manner."
Acevedo also confirmed that the gunman's weapon was an AK-47 but declined to say how many shots were fired.
After UT officials lifted the campuswide lockdown, the area around the library remained sealed as investigators concentrated on two general crime scenes -- the section of the library where Tooley took his life and other sections of the campus where shots were fired. Police were seen picking up shell casings on a sidewalk hours after the incident.
More than 51,000 students are enrolled at the campus several blocks north of the state Capitol in central Austin. UT officials said the only metal detectors are on the ground floor of the UT Tower in response to terrorism fears after 9-11.
"It could have been a whole lot worse," Dahlstrom told the Star-Telegram. "We have no idea what his motive was. We're very fortunate."
Several students captured the drama on their cellphones, and text messages flew among students as they remained holed up in university buildings.
Rachelle Simon, an architecture major from San Antonio, said she was in class across the street from the library when students began receiving text warnings through the university alert system.
"At first people were a little unsure of what was going on but as more information arose, people got a little more tense," she said. "Then some of the police showed up and people from the SWAT team were there. That's when people really got anxious because they began to realize the drama of the situation."
Authorities credited a recent joint training program by Austin police and UT for helping them to be prepared for just such an emergency.
"The purpose of this training is to respond to these types of incidents," Dahlstrom said. "The training paid off in this situation and probably prevented a much more tragic situation."
Staff writers Bill Miller and Max Baker contributed to this report.