no you cant when it says use a shield it means use the sheild and a pistol while holding the pistol click the left click on the mouse and if were lucky it will shoot.
I think I know what map u are on. not sure though.... newayz I found this a good method. when u start off, buy the stuff and run quickly to the small door infront on the right and go through the large door, Go to higher level and in many cases you will find some guys here,Otherwise jst continue through the rooms and u'll find a Large door, Ignore this and go left and u'll come up to another large door. Go through here and u should find a couple of those terrorists most of the time....
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If you want to know methods to use it I know 2.... I recommend using the Nighthawk pistol as it packs a massive punch, though remember that the bullets run out pretty quickly.
1) Hold the sheild infront of you using right click, then carefully look at the guy, his name should flash, now quickly undeploy using right click and shoot like crazy at the guy till he dies...
2)Deploy the sheild and keep running sideways around him,at a good moment of time undeploy and unload bullets on him... p.s. - Its really helpful if he has his attention on another of you players.....
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