Please, we don't know what actually triggers the event, that certainly doesn't mean that nothing triggers it. Since this has devolved into a semantical discussion, it would be more correct to say that there is nothing we know of that causes the event.
We know more than you think. Per quantum mechanics, we know what the event is. It's not simply a dearth of knowledge, it's not that we don't know what caused it, but rather we know it is uncaused. It arises from uncertainty principles and genuine limits on what can be known - again, it's not that we
could know but as yet don't, it's that we
can't know. The quantum world places hard limits one just how much we can know, not because of technological limits, but because that knowledge simply doesn't exist. The nature of the wavefunction is such that it allows particles to spontaneously exist outside of where we had previously measured them to be - they can tunnel out of potential barriers.
Again, that seems to be a semantical argument. Your statement above is not entirely accurate. You don't just need any atom. It's not like this event takes place in all atoms. Certain conditions must exist in the nucleus of atoms in which this event takes place, conditions that would be considered abnormal as far as nuclei go and therefore would have to be considered a "cause". Now if you want to change the language to suit your argument and call this "allow", go ahead, but the fact remains that there is a cause and that is the tension that exists due to the imbalance. SInce, without this tension the event would not take place, it should be considered a "cause". Furthermore, there is a root cause and that would be either the formation of the element through a stellar event or by the mutation of the element by the bobardment of cosmic radiation.
You can call that the 'cause' if you want, but that is simply and utterly uninteresting.
By your definition, the cause of the man's death is the gun manufacturer, and the Second Amendment, and the sexual intercourse had by the man's parents 30-odd years ago. These are things which transpired, and without them the event couldn't have happened, and so, according to you, are the various causes of his death. But we don't care about those things. On one hand, there is a fundamental difference between what you call the 'cause' of death (his parent's having sex), and the
real cause that everyone is actually interested in: the actual physical event which made him go from life to death - the destruction of his brain when the bullet ploughed through it. That's the cause of death.
And on the other hand, to repeat myself, it's uninteresting. What's interesting is an event which spontaneously happens (e.g., quantum tunnelling). Whether or not previous events have transpired to set up this random event isn't interesting. What's interesting is the actual event itself.
When the apple fell on Newton's head, we care that the cause was gravity, not the Big Bang.