A man wearing a ski mask opened fire with an AK-47 inside a University of Texas library Tuesday morning, then fatally shot himself, police said. Police ended their search for a possible second suspect early in the afternoon, saying authorities believed the gunman was a student at the university and that he had acted alone. The nearly 50,000-student campus — whose clocktower was the site of one of the nation's deadliest shooting rampages four decades ago — had been on lockdown while officers with bomb-sniffing dogs carried out a building-by-building manhunt. Campus police spokeswoman Rhonda Weldon said a man fired an automatic weapon on the sixth floor of the Perry-Castaneda Library, then shot himself dead. Austin Police Chief Art Acevedo said the weapon was an AK-47. Acevedo said police were investigating what he described as a second crime scene outside the library where shots also were fired. Campus police Chief Robert Dahlstrom said officials later ruled out the possibility of a second shooter, explaining that the initial confusion came about because the gunman had fired shots in multiple locations. He said the suspect wore dark clothes and a ski mask. 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.