How do I change a particle angle?

I'm making a Top-Down Shooter game, and when I shoot the enemy, it spawns a particle (blood), but its always the same angle.

I want to make it rotate depending on the angle that I shot the enemy.

Example:

When I shoot the enemy and I'm ABOVE him, the blood will splatter DOWN.

or

When I shoot the enemy and I'm BELOW him, the blood will splatter UP.

When hitting enemy, you need to set it's angle to:

angle(bullet.x,bullet.y, enemy.x,enemy.y)