Need help shooting from front

Im attempting to make an overhead shooter game. Ive got the basic movement down already, and rotation towards mouse. For when he shoots, ive set it to duplicate a bullet movie clip, but i only understand how to set it towards one graphical direction(ex: x +, y -)

The code i know ive gotta fix is

onClipEvent (enterFrame) {
this._x += laserMoveSpeed;
if (this._x>1000) {
this.removeMovieClip();
}
}

The little x + part has to be fixed, but i have no idea what to substitute in order to make it shoot from the front.

If anyone could even lead me in the correct location, that would be great, ive been actionscripting a bit under a month only =[