For the younger kids: the round green object that the military men drop is called a grenade. A grenade is a weapon used in war that is thrown at the enemy, and it explodes.
Why was it dangerous for the kid to try to hit the grenade with his bat?
The grenade could explode, which would hurt and maybe even kill the people who were close to it.
Did the adults who were watching realize the danger?
Yes, they recognized that the boy was playing with a grenade.
Also, the warnings and reactions of the military men made everyone believe it was a real live grenade.
What did the adults do when they realized what was happening?
They called to the boy to stop.
Some approached the boy and tried to take away the bat or the grenade.
The military men jumped to the ground to protect themselves in case the grenade were to explode.
Why do you think that the adults who, despite the danger, still tried to stop the boy, could be called heroes?
They were willing to sacrifice themselves, their health or even their own life, to try to protect the boy from the grenade.