"I was actually quite surprised that a lot of the settlers' comments were that they were stunned, shocked, and saddened," she said. "But in my own life, in my family's life, this is known."
The letter has been shared more than 5,000 times on Facebook and Twitter, and while most people have reacted with shock, McAdam said some have also been dismissive of the painful history.
"People were saying 'get over it,' but they don't realize this didn't end until approximately 1959."