Authorities have said a grand jury would review the shooting to determine whether charges should be filed. Such investigations are typical in police shootings in Alabama.
Mobile County Sheriff Sam Cochran has said it was unclear whether the officer could have done anything other than shoot Collar because he walked outside with his gun drawn.
He told reporters earlier this week that the officer may not have had time to holster his gun and use another weapon "because the events were evolving so rapidly and he was so close that had he put the pistol in the holster I don't know that he could have drawn something else," Cochran told reporters earlier this week.
Cochran said he believed it was proper for the officer to go outside with his gun drawn after Collar repeatedly banged on windows at the campus police station, but he hasn't said whether he thought the shooting was justified.
Authorities haven't said why Austin drew his gun first rather than opting for a less-lethal weapon. Collar managed to get up even after being shot once in the chest, and backup officers arrived seconds after the shooting.
An attorney for Collar's family, former Alabama Lt. Gov. Jere Beasley, said there was nothing to justify the shooting on the surveillance video, which was shown to both the media and representatives of Beasley's law firm but has not been released publicly.
Collar's funeral is scheduled for Saturday in his hometown of Wetumpka, located about 20 miles north of Montgomery.
The university police department has 33 sworn officers, Ayers said. Members are required to meet the same type of minimum training standards as officers in a typical municipal or county department, but the school hasn't released details on Austin's training.