One of the servicemen, according to law enforcement officers, allowed the child to pick up a loaded RPG-26 anti-tank grenade and pull the trigger.
The shooting injured at least nine people, six of whom were children.
A two-year-old child received the most severe injuries, he had a shrapnel wound to his face and a complex injury to his hand.
The Chernihiv city council noted that the explosion occurred near the regional art museum named after Galagan on August 3 at about 13.30.
Official permission for the military to hold this exhibition was not provided to the city authorities.
A charity fair was held in the park area and a demonstration of weapons became part of this event.
Suspicion from the State Bureau of Investigation was received by two servicemen: the commander, who ordered subordinate servicemen to bring weapons to the exhibition for demonstration, and the serviceman, who gave the child a loaded weapon.
Employees of the DBR detained the suspected servicemen and filed a petition with the court for a preventive measure in the form of detention.
The servicemen are suspected of violating the rules for handling weapons, which resulted in bodily injuries to several people.
They face a sentence of up to ten years in prison.
A motion will be filed with the court to elect him a measure of restraint in the form of detention.