Bovsun v. Sanperi (61 N.Y.2d 219 [1984]) held that "where a defendant negligently exposes a plaintiff to an unreasonable risk of bodily injury or death, the plaintiff may recover, as a proper element of his or her damages, damages for injuries suffered in consequence of the observation of the serious injury or death of a member of his or her immediate family assuming, of course, that it is established that the defendant's conduct was a substantial factor bringing about such injury or death" (id., at 230-31.) This "zone-of-danger rule . . . is premised on the traditional negligence concept that by unreasonably endangering the plaintiff's physical safety the defendant has breached a duty owed to him or her for which he or she should recover all damages sustained" (id., at 228-29), including emotional distress resulting from both the fear for one's own safety and resulting from the observation of an injured family member (see id., at 228, 231 n 10.)