The player uses different attacks that are attached to the weapons. Or could be simply added to the scenery as enviromental hazards. These components use an auxiliary HitBox component which should always operate on the Combat layer.
These attacks, use an asset of type AttackType. These types indicate which Damageable types are affected by the attack and how much damage it inflicts.
Attack types can be created from the Project panel by right clicking and selecting:
Create→Horror Engine→Combat→AttackType
Apart from the MeleeAttack and ShotAttack used by the player weapons, the engine also provides a simple attack component that will be performed on Overlap named OnOverlapAttack.
Check the prefab EnemyPlaceholder as an example of how Damageable and a simple Attack have been setup