Jaquez Myrick, 25, of Montgomery, was taken into custody while leaving the scene of the Tuskegee University shooting, the Alabama Law Enforcement Agency said.
The agency said Myrick faced a charge of possession of a machine gun.
An 18-year-old man who died was not a university student but that some of the injured were students, authorities said.
Twelve people were wounded by gunfire, and four others sustained injuries not related to the gunshots, the agency said earlier. Their conditions were not immediately released.
The FBI joined the investigation and said it is seeking tips from the public, as well as any video witnesses might have. It set up a site online for people to upload video.
The shooting happened as the historically Black university's 100th Homecoming Week was winding down.
Tuskegee University announced that all classes on Monday have been cancelled. Grief counsellors will be available to help students in the university's chapel.
"The parents of this individual have been notified. Several others including Tuskegee University students were injured and are receiving treatment at East Alabama Medical Centre in Opelika and Baptist South Hospital in Montgomery," the university said in a statement.
An autopsy on the 18-year-old was planned at the state's forensic centre in Montgomery, Macon County Coroner Hal Bentley told The Associated Press.
City police chief Patrick Mardis said the injured included a female student who was shot in the stomach and a male student who was shot in the arm.
Police were responding to an unrelated double shooting off campus when officers got the call about the university shooting at the West Commons on-campus apartments, Mardis said.
"Some idiots started shooting," he told the news site Al.com. "You couldn't get the emergency vehicles in there, there were so many people there."
Sunday's shooting comes just over a year after four people were injured in a shooting at a Tuskegee University student housing complex.
In that shooting, two visitors to the campus were shot and two students were hurt while trying to leave the scene of what campus officials described as an "unauthorised party" in September 2023, the Montgomery Advertiser reported.
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