So you could always use the animated sprite itself, assuming you're using the "mirrored" option to flip your sprite right and left when you move in those directions.
--if animated sprite is mirrored = used left shoot animation
--if animated sprite is not mirrored = use right shoot animation
If this isn't what you've done, for simplicity's sake, you may want to try implementing it (there should be some tutorials that have information about animation and mirroring sprites available in the tutorials area). Otherwise you could have a variable for whether the character is facing right or not that can be set to true or false depending on whether the right or left movement buttons are pressed and use that, but unless you're moving your person in all sorts of crazy ways, that's probably overkill.