"The injury does not appear life-threatening at this time," McMenamin said.
Mayor Scott Evans said the student shot as he crossed the street outside the Viking Academy School, an alternative school that has about 240 students grades 7-12.
He said many students had already left the building for the day, but school was locked down for a time.
A few minutes later, Evans said, a police chase a few blocks away ended with the arrest of a male found with a gun and marijuana.
Not long after, he said, another man was fatally shot in the head on Central Avenue. Evans said a suspected gunman was quickly arrested.
The mayor said police are looking into whether the incidents are connected.
McMenamin said the shooting near the school came after two people got into an argument and one person pulled out a weapon and fired.
McMenamin said police didn't yet know what sparked the argument.
McMenamin said police were trying to determine if the shooter was a student.
"We're still trying to develop information regarding the shooter," she said.
She said spent shells have been found.
The Atlantic City shooting comes a day after a 10-year-old accidentally fired a gun at Linden school.
No one was hurt in that incident but the fourth-grader faces two weapons possession charges.
Elsewhere, a first-grader prompted a scare Thursday on a Millville school bus with a toy gun. Police responding to reports that a bus driver had taken a handgun from a 6-year-old found the weapon was fake.
