You can narrow it down by again picking the monster instance with UID targetUID for the overlap check. Or you can do something like checking if the instance with that UID still exists. The latter would be useful if in your game you have to destroy the bullet early before it reaches its destination by checking while bullet 'is moving' if that instance exists.
And yes of course you would need an event for when there is a monster there on arrival. Not sure how your game works but if it's possible then you need to plan for that.