[SmG Nukem]

That sort of thing happens all the time in Australia. Some gum trees drop their branches all the time. Most people that go camping are aware of this so they don't put their tents under branches. Still people forget that the nice shady tree they park their car under has a tendency to do this.
It doesn't even need to be a storm just a windy day most of the time. Every now and then the tree just drops it's branch without any help from the weather at all, it just gets boring insects/animals that weaken the branch until it can't hold it's own weight.