As far as I know to fire an event with an action button, that event must be set the same as character, is there a way to put it below the character and it still fires the action button?
...yes? The event priority and the event trigger are two separate selections on the event screen. You can set them to whatever combination you like.
The only caveat is, as arsMori said, if the priority is below character, they must be standing on, rather than adjacent to, the event to trigger it with the action button.
If you specifically want the character to be able to walk on top of the event but trigger it from an adjacent space, you should leave the priority as same as character but check Through on.