Turret and Target

Hello! I apologize for my English.
There are blueprints of the turret, which monitors the goal. When entering into a spherical target collision, it begins to rotate the turret and shoot her. But the problem arises when the collision part of the second goal. In this case, the first target is complete ignore.
Just Sentry ignores the second purpose is that collides during the first attack.
If the way to explain the turret, it is necessary to attack targets in turn and to their complete destruction? (While they are in conflict)

My sceenshoot -

I used this example to solve the problem, but the problem persists - Turret Tutorial | Shooter Tutorial

Please! Help with a solution to this problem!