Between 1987 and 1990, McDowall et al. found that guns were used in defense during a crime incident 64,615 times annually (258,460 times total over the whole period).[44] This equated to two times out of 1,000 criminal incidents (0.2%) that occurred in this period, including criminal incidents where no guns were involved at all.[44] For violent crimes, assault, robbery, and rape, guns were used 0.83% of the time in self-defense.[44] Of the times that guns were used in self-defense, 71% of the crimes were committed by strangers, with the rest of the incidents evenly divided between offenders that were acquaintances or persons well known to the victim.[44] In 28% of incidents where a gun was used for self-defense, victims fired the gun at the offender.[44] In 20% of the self-defense incidents, the guns were used by police officers.[44] During this same period, 1987 to 1990, there were 46,319 gun homicides,[45] and the National Crime Victimization Survey estimated that 2,628,532 nonfatal crimes involving guns occurred.[44]