I didn't look at your capx, but here's on possibility:
Basically the first step is do a laser. Here used a sprite that is stretched from the gun to the wall. Then a new laser is created at the end and it's angle is set to the reflecting angle. In the link the direction is stored as a x difference and a y difference, then to bounce against a vertical wall the dx is negated. In a similar way horizontal walls are handled. The actual angle can be calculated with the angle expression.