Police do not know how the confrontation began, but "we do not believe at this point the 18-year-old was armed", Hoover police Capt. Gregg Rector said.
"We are working closely with the Hoover Police Department", a spokesperson for the mall said in a statement.
AL.com reports that several shoppers were seen with their personal guns drawn.
"Unfortunately, if you get thousands and thousands of people together in any venue, occasionally you're going to have violence", Rector said. A 12-year-old girl who happened to be nearby was also shot. She was reported in stable condition at Children's Hospital.
He said the Galleria is one of the safest shopping destinations and that in the mall's 33-year existence, he could count the number of people shot on the property on one or two hands.
According to the Riverchase Galleria website, the mall was scheduled to open until midnight (local time), and was scheduled to open at 6:00 a.m. for Black Friday shopping.
The shooter fled but was confronted and shot dead by police with the second teen rushed to hospital in a serious condition.
The Jefferson County Sheriff's Office is investigating the case per the request of the Jefferson County District Attorney's Office. I'm so shaky right now I'm sorry if I don't make any sense.
Officials said there had been extra officers at the mall Thursday night as a precaution.
"This was my first Black Friday", the high schools senior said.
Reports of gunshots quickly spread, but they were deemed false and no one was shot.
Footage emerged a year ago of women punching and kicking each other before being handcuffed by police.