Authorities are trying to determine how the boy got the gun inside the K-8th grade school, which has a metal detector in the front entrance, and many parents are concerned about the lack of notification.
Police say the boy had the 22 caliber gun in his backpack, which was in his locker. The gun was unloaded when school staff recovered it Wednesday, according to the state's attorney's office, but there were 33 Hollow point bullets in the backpacks.
It's believed the gun belonged to a member of the boy's family, and he hadn't brought it to school to do any harm. The boy was taken into custody Wednesday afternoon and cited as a juvenile for unlawful use of a weapon, but some parents say they were unaware of the incident.
"We should have been notified as soon as it was found out," Sylvia Campos, grandparent, said.
"We didn't know. We found out by other people. They didn't let us know, and it happened yesterday. They should have told us something," Irma Nevarez, parent, said.
Nevarez was so distressed that she and some other parents came John Marsh Elementary to withdraw their children from school until they could get answers.
"I find out when a lady called me and [she] told me, and I said, 'What happened on what?'" Aqueda Rodriguez said.
"Most parents are finding out about it now and that's unacceptable," Juan Quintana, parent, said.
Complaints about the lack of notification brought Chicago Alderman John Pope, 10 Ward, to the school on Thursday.
"There's a number of avenues we can take," Pope said. School officials say the details didn't come together completely until later in the day and they wanted to make sure that their facts were straight before releasing anything.
The principal at John Marsh Elementary invited parents to a special meeting on Friday and students left school Thursday with a note to parents, which includes a general description of the event and a pledge to review and modify building security.
The 13-year-old boy appeared in juvenile court Thursday. He was released into his mother's custody despite objection from the state. He faces possible expulsion.