protected void OnTriggerExit(Collider other)
        {
            var character = other.gameObject.GetComponent <Character>();

            if (character != null)
            {
                // Check just in case the player object has more than 1 collider.
                if (_charactersInRange.Contains(character))
                {
                    character.NotifyWentOutOfTriggerRange(_trigger);
                    _trigger.UnUse(character);

                    _charactersInRange.Remove(character);
                }
            }
        }