You hear fire departments, and anti-gun organizations like newspapers, routinely state things like “cooked off” ammunition is dangerous. The likelihood of being hurt from a round of ammunition “cooked off” in a fire is magnitudes of danger less than your normal fire situation. Unless a cartridge (round of ammunition) is actually partially contained (like in a barrel), it’s not going to achieve any significant velocity. Indeed the laws of physics make it so that the bullet itself is hardly going to move. The now empty brass casing is going to become the “projectile.”
The Tempe Police Department’s Explosive Ordinance Detail responded to the scene due to the explosions caused by the ammunition and fireworks. The fire is under investigation, but it is believed to be an electrical fire, Reichling said.
In this case, the fireworks were by far more dangerous than the rounds of ammunition.
Read the whole “article” in the Arizona Republic.