Live streaming coverage of the shooting from CBS affiliate KEYE:
Police have identified the man who opened fire on the University of Texas campus before killing himself as a 19-year-old student from Austin.
Police said Tuesday that the gunman was Colton Tooley. College records indicate Tooley was a sophomore math major. His parents did not immediately respond to a message left by The Associated Press.
Campus police said earlier in the day that a man fired an automatic weapon on the sixth floor of the Perry-Castaneda Library, then shot himself dead.
Campus police Chief Robert Dahlstrom said at a Tuesday news conference that officials have ruled out the possibility of a second shooter. He says there was initial confusion about the number of suspects because the gunman fired shots in multiple locations.
The 50,000-student campus — the site of one of the nation's deadliest shooting rampages four decades ago — was on lockdown while officers with bomb-sniffing dogs carried out a building-by-building manhunt.
Acevedo told a news conference that police are investigating what he described as a second crime scene outside the library where shots also were fired.
Randall Wilhite, an adjunct law professor at the university, said he was driving to class when he saw "students start scrambling behind wastebaskets, trees and monuments," and then a young man carrying an assault rifle sprinting along the street.
"He was running right in front of me ... and he shot what I thought were three more shots ... not at me. In my direction, but not at me, clearly not at me," Wilhite said.
The professor said the gunman had the opportunity to shoot several students and Wilhite, but he did not.
No shots were fired by law enforcement, Acevedo said.
The university canceled classes for the day. Police and university officials locked down the campus for several hours and early afternoon started to allow students to leave.
In an e-mail alert to students and staff, the university said police were searching for possible second shooter.
Weldon said there was no report that the possible second suspect may have been armed, but that police are taking all precautions and keeping the campus locked down.
Law enforcement from campus police, Austin police and the state Department of Public Safety rushed onto campus at the first reports of the shooting. Tank-like armored vehicles were positioned near the library. A DPS helicopter circled the campus overhead.
Jennifer Scalora, who works in admissions, was in her office about 100 yards from the library. She said the campus — one of the biggest in the country — was now empty except for police, SWAT teams and helicopters.
"Campus is very quiet. You can barely see anyone moving," Scalora said.
"The students did their part, they cleared the streets, they cleared the grounds in a very quick manner," Acevedo said.
Tuesday's shooting is not the first at the school.
On Aug. 1, 1966, Charles Whitman went to the 28th floor observation deck at the UT clock tower in the middle of campus and began shooting at people below. He killed 16 people and wounded nearly three dozen before police killed him about 90 minutes after the siege began.
The Perry-Castaneda Library is one of several on the campus and is one of the busiest undergraduate libraries.
Student Joshua Barajas, 23, said he usually is in the library in the mornings but was delayed Tuesday when he made a rare pit stop for coffee.
"These little mundane decisions could save your life. If I hadn't stopped for coffee — and I never stop for coffee because it's $4 — I could have been in that building," Barajas said. "It's creepy. I don't even want to think about it."