Natural disasters

A group of four prisoners were held captive by the enemy and each prisoner was to be shot each day through the week. As natural disasters were common in this specific part of the world, the group of prisoners decided to make up a plan of distracting the guards. Before each prisoner would be shot, they would shout out a natural disaster, which would cause chaos and distract everyone to give enough time for each prisoner to escape. As three days passed the first three prisoners escaped by shouting out their chosen natural disasters and running away, however the final prisoner shouted out a disaster and was shot dead on the spot.
What was the natural disaster he shouted?