The University of Texas was put on lockdown through Tuesday afternoon, after a masked gunman opened fire in the campus library and eventually shot himself dead. No one else was injured.

The incident began Tuesday morning and continued through the early afternoon, as police searched for a second suspect. Authorities later said they believed the gunman -- whose name has not been released -- was a student at the school and acted alone.

Witnesses said the gunman didn't appear to be aiming at anyone as he fired shots from his AK-47.

"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," adjunct professor Randall Wilhite recalled.

He added that the gunman had the opportunity to shoot several students, but did not.

This wasn't the school's first shooting incident.

In 1966, Charles Whitman shot and killed 16 people from the observation deck at the UT clock tower. Nearly three dozen others were wounded before police killed him more than an hour after the shooting began.

The University of Texas has about 50,000 students.