-Add the bullet behaviour to the bullet
-When you spawn the bullets set Sprite.bullet.Angle_of_Motion, which normally will be something like:
angle(Boss.X, Boss.Y, Player.X, Player.Y) + maybe some variance to spread the bullets
-Also, you could add image points on the boss if you have a specific point on the boss that you want the bullets to spawn from, then you can use the same set angle of motion but this time referencing the image points.
angle(Boss.imagepointX("Name"), Boss.imagepointY("Name"), Player.X, Player.Y)