Authorities stated that the suspect had previously worked at the store and had a history of criminal activity.
Another male, 16, was critically wounded and a male, 15, was seriously wounded as they walked from Senn High School at dismissal.
Two vehicles, a dark-colored sedan and a sport-utility vehicle, pulled up along Wabash Avenue.
Two firefighters have sustained injuries, and an ambulance is on the way.
The second man, aged 32, sustained injuries to the leg and torso, currently in critical condition.
At present, no one is in custody, and the investigation is being handled by Area One detectives.
Family members confirm that Lopez was a dedicated special education teacher at Nathan S. Davis Elementary School in Brighton Park.
$15K reward offered for info leading to arrest.
It occurred due to an accidental trigger.
Security and SWAT teams are conducting a thorough sweep of the school to locate it.