You can shoot down terrorists who invade your base in Sniper View mode.
You can access Sniper View mode by tapping on Command Post > Sniper View. Rewards can be obtained by killing terrorists in Sniper View.
Tap the scope to snipe and the screen to fire.
※ You get a free set of ammunition per day.
After this, you can buy them with gold or at the Alliance Store.
※ If you have the officer 'Ying Yue', rewards will increase depending on the her promotion level.