Grady spokeswoman Denise Simpson said the victims there were in stable condition with wounds that were not life threatening. In addition to the three shot, one person injured in the panic was brought to the hospital, she said.
The event attracted 826 tweets a minute on Twitter with the biggest spikes when Mr Cameron was accused of "scaremongering" by self-employed Essex woman Denise Simpson and during his exchange with Ms Bouazzaoui.
The wounded boy was taken "alert, conscious and breathing" to Grady Memorial Hospital, said police spokesman Carlos Campos. Grady Heath System Spokeswoman Denise Simpson said the teen had been discharged from the hospital Thursday night. Campos said charges against the shooter were pending.