stuck at mdk2 level

[they call mr big]

ok I'm at the first level and I'm up to the boss, sniped out the those blue balls things in the middle of that huge gun, now what am I suppose to do???

 

[DARRIN]

Trying to remember, its been a long time. Is this where he is up in the air in a big ship looking thing? You must snipe all the balls and the center of the ship will open up exposing the boss and then you can snipe him.