Hi ,
The best approach would be to deconstruct the BP_Security_Camera_Tracking asset from the BlueprintExamples project. You can break down the movement of the parts in the same way that a turret would move and track the player, but change the Alarm state to a firing state. You can fire bullets by using a Spawn Actor from Class node.
I hope that this helps you with your blueprint. Let us know if you need further assistance.