Flunitrazepam, widely known by its trade names (e.g. Rohypnol), may cause severe violence, especially in combination with alcohol. Flunitrazepam abusers become cold-blooded, ruthless and violent, and do not remember their violence. Reputedly it is supplied to professional hit-men and enforcers by their bosses to promote ruthless efficacy. One case report describes how a young man, intoxicated with flunitrazepam and involved in causing serious knife and gunshot wounds and taking hostages, felt so invincible that he openly challenged the police, threatening them with an assault rifle, but was himself shot. Flunitrazepam may exert pharmacological effects on GABA-ergic systems, thus lowering serotonin levels. The impulsive execution of violent crimes and suicide attempts in which a violent method (hanging, shooting, self-stabbing) has been used are associated with the presence of low serotonin levels. It is therefore recommended that flunitrazepam should be classified as a controlled substance in Sweden as it is elsewhere.