Shooting helicopter in pygame

Question

I'm trying to make a game using pygame module I've already imported my pictures and can move the helicopter but I'm not able to shoot. The commented lines are the things that I've done so far for the shooting part. When pressing the button for shooting, nothing happens. It seems that the code does not run for the second if statement and I don't know the reason.

Thank you for your help!

import pygame

white=(255,255,255)
black=(0,0,0)

pygame.init()
surface = pygame.display.set_mode((1000,1000))
pygame.display.set_caption("AI Game")
clock = pygame.time.Clock()

def helicopter(x , y, image):
    surface.blit(helicopterPicture ,(x,y))

def bulletshape(x, y, image):
    surface.blit(bulletPicture ,(x,y))

bullets=[]



helicopterPicture = pygame.image.load('helicoptter.png')
bulletPicture = pygame.image.load('bullet.png')

x_helicopter= 150
y_helicopter= 200
x_bullet= 260
y_bullet= 240
y_move = 0
x_move = 0
y_bullet_move = 0
x_bullet_move = 0

Game_Over=False

def GameOver():
    pygame.quit()
    quit()


while not Game_Over:
    for event in pygame.event.get():
        if (event.type == pygame.QUIT):
            Game_Over=True
        if (event.type == pygame.KEYDOWN):
            if (event.key == pygame.K_UP):
                y_move = -5
                x_move = 0
                y_bullet_move = -5
                x_bullet_move = 0
                if (event.type == pygame.KEYDOWN):
                    if(event.key == pygame.K_SPACE):
                        y_bullet_move = -20
                        x_bullet_move = 0

        if (event.type == pygame.KEYDOWN):
            if (event.key == pygame.K_DOWN):
                y_move = 5
                x_move = 0
               # y_bullet_move = 5
               # x_bullet_move = 0
               # if (event.key == pygame.K_KP_ENTER):
                #    y_bullet_move = 10
                 #   x_bullet_move = 0
        if(event.type == pygame.KEYDOWN):
            if(event.key == pygame.K_RIGHT):
                x_move = 5
                y_move = 0
                x_bullet_move = 5
                y_bullet_move = 0
                #if(event.key == pygame.K_KP_ENTER):
                 #   x_bullet_move = 10
                  #  y_bullet_move = 0
        if(event.type == pygame.KEYDOWN):
            if(event.key == pygame.K_LEFT):
                x_move = -5
                y_move = 0
               # x_bullet_move = -5
               # y_bullet_move = 0
               # if(event.key == pygame.K_KP_ENTER):
                #    x_bullet_move = -100
                 #   y_bullet_move = 0

    y_helicopter+=y_move
    x_helicopter+=x_move
    x_bullet+=x_bullet_move
    y_bullet+=y_bullet_move

    surface.fill(black)

    helicopter(x_helicopter,y_helicopter,helicopterPicture)
    bulletshape(x_bullet,y_bullet,bulletPicture)

    if (y_helicopter>950 or y_helicopter<25 or x_helicopter>950 or x_helicopter<25):
        GameOver()

    pygame.display.update()
    clock.tick(10)


pygame.quit()
quit()