Ammunition cooking off in a fire is not terribly dangerous as it is not confined in a steel tube. The casing will go farther than the bullet as it is lighter weight and neither will fly very far as the energy will be more sideways than fore and aft.A building burned here several years ago, a storage units building that had one unit full of ammo. The firemen did their job as if it were any other building fire. No one was hurt and the sounds of the ammoo burning off were muted as the force was expended in all directions and the force was dissipated for the same reason.
More likely a brass tube “case”