Excessive sweating and unconsciousness after seeing some one badly injured

Patient: Hello, i dont really know what it is but when i see some one injured,some one stubbed by knife,a car accident where some one is injured or even some one talking about his past experience like how painful it was when he fall from a tall building and broke his leg, etc, then i cant control my self i experience excessive sweating and lose control of my self and become unconscious for a while. i hope i have provided the info needed.