How do I fix 2D aiming?

I'm making my first game and it is 2D and I want the character to be shooting the way that he is facing (left or right). Shooting 'right' is perfectly fine but when the character is facing left, the bullets still go right. How can I fix this?

How do you have your events set up to fire the bullet? You should be able to do a "if player is mirrored, then set bullet movement angle to 180" type of event, assuming you're just mirroring the players sprite for left and right movement.