In the case of the Native women I knew, most of the assaults were committed by family members and "friends" of the family on the Reserve. Friends and family are the people least likely to be reported by a rape victim, for a great many obvious reasons. A rape victim is more likely to report an assault by a complete stranger.

There were also some assaults of those girls by their foster parents (several different foster parents over a period of maybe 8 or 10 years). Whether the foster parents were Native or White seems to have had little bearing on the issue.

It's a case of the illegitimate use of power. Those who have power, and who have little idea or inclination to use it responsibly, are those who may commit rape or assault.