Maddox Derkosh fell from a wooden railing overlooking the African wild dog exhibit at the zoo last Sunday. Investigators are still trying to determine how it happened.
The boy's death has sparked an outpouring of support. Strangers are donating toys trucks instead of flowers at the request of the boy's parents. Some 3,000 have been donated already.
The family plans to give the trucks to a charity that will distribute them to needy children on Christmas.