University officials announced on their website that campus police had arrested one male suspect and were searching for another in the robbery at gunpoint of a student.
The victim had invited the men to his room when they robbed him of $1,000 and a cell phone and fled, the statement said. A shot was fired but no one was apparently injured.
Officials believe the second robber left campus. Neither suspect apparently attends the school.
The Mobile campus sent out an alert at about 3 p.m. CDT advising students to stay indoors after receiving a report of an armed robbery at the Delta 4 residence hall.
Officials announced at about 8:45 p.m. that the lockdown had been lifted and an arrest had been made.
The school late Sunday urged students to "resume your normal activities but remain cautious and report any suspicious activity."
The school had used loud speakers, emails and a dial-in phone system to advise students to seek shelter and stay indoors.
"We did in fact do a campus lockdown," said university spokesman Keith Ayers.
The initial crime alert said "there have been reports of someone on campus armed with a weapon last seen in the housing area."
The alert went on to advise the university community to "remain inside until further notice."
