How do you beat nocturnal on sniper assassin 4

The mission "nocturnal" is the 13th and last level on Sniper Assassin 4.

There are three levels, and your targets are guys trying to kill Charlie as she escapes in the dark. There are three floors including the one she is on. You can have an easier time if you shoot out some of the windows first and whenever you have time. The guys with knives and axes can be shot nearby, but the ones with pistols can strike from farther away.

-- Third Floor: shoot the rope that Charlie is hanging from, then move right as she walks, killing 3 attackers. As she crosses a post, 1 sneaks up behind her, so kill him, 2 ahead of her, and 1 more behind her. Then 1 more from the front finishes the floor as she makes it down the stairs.
-- Second Floor: Pan left and shoot both ropes holding the board, which covers the open hole in the floor. As she crosses, 2 guys emerge from the left, one with an ax and one with a pistol. Shoot both, then quickly 1 more with a pistol behind her to the right. As she nears the stairwell, 1 with an ax will leave it and hide behind the post*. Shoot him before he gets there, then swing far right to get 1 more guy with a pistol. She reaches the stairs.
-- First Floor: As she moves right, kill 2 guys. As she crosses the post, 1 comes behind her. Shoot him, then rapidly go right to shoot 2 guys with pistols. One last guy comes from behind her and this completes the mission.

* It is possible to shoot the guy behind the post, but not as easy.