Phoenix Police say the incident happened just after 1 p.m. on Aug. 28. After finding the gun, school administrators secured it before officers arrived at the school, which is located near Liberty Lane and 24th Street.
Once at the school, officers retrieved the gun and began their investigation. The child's parents are cooperating with police and no arrests have been made.
"Once the investigation is complete, the case will be submitted to the Maricopa County Attorneys’ Office for consideration for appropriate charges," Sgt. Robert Scherer said.
No further details were released.
Map of where the school is located: