
Unlikely.  Ammunition is not as dangerous when simply burned as it
is when fired from a gun.  The brass case is not capable of holding
the pressure generated by burning powder, and will (unless supported
by the walls of a gun barrel or chamber) simply split open.  While
this may cause small pieces of brass to fly around, it will not
propel the bullet with any significant velocity.

In fact, it was not uncommon in years past to dispose of old loaded
cartridges by burning them.  As long as you were not close enough
to take a piece of flying brass in the eye, you were reasonably safe.

Thus, the detonation of loaded magazines or loose rounds might cause
slight injury but would be unlikely to cause fatal bullet wounds.