Between 1987 and 1990, David 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). 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. For violent crimes, assault, robbery, and rape, guns were used 0.83% of the time in self-defense. 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. In 28% of incidents where a gun was used for self-defense, victims fired the gun at the offender. In 20% of the self-defense incidents, the guns were used by police officers. During this same period, 1987 to 1990, there were 11,580 gun homicides per year (46,319 total), and the National Crime Victimization Survey estimated that 2,628,532 nonfatal crimes involving guns occurred.