Warning: This story contains disturbing language.

In an angry letter signed by “friendly neighbours,” a group of home owners in an Alberta condo community appear to threaten children and tell a family to “Go back to the reserve where Indians belong.”

An image of the anonymous letter spread quickly when a St. Albert mother of three, Katrina Anderson, posted it on Facebook. Her 12-year-old daughter found it in their mailbox on Monday.

“Move out or things will escalate,” the letter reads. “Would not want to see the kids getting hurt. This isn’t a reserve.”

Anderson’s daughter called her in tears after reading the letter.

“I couldn't believe what she was reading me. It was absolutely disgusting,” Anderson said. “I've experienced racism, but nothing like this. This isn't happening on the playground. It's not happening out in public. This is in our mailbox. This is our house.”

Despite reporting the letter to the RCMP on the advice of the condo board, the family has decided to pack up and move out of Grandin Woods Estates.

“My kids can't be here. That's the bottom line,” she said.

After posting the letter on Facebook, it eventually reached St. Albert mayor Cathy Heron. “Your first reaction is horror, and ‘This is a black cloud over St. Albert,’” she said in a phone interview with CTV Edmonton. “But if you read all the responses -- they're all supportive.”

Neighbours who spoke with CTV Edmonton were shocked to read the contents of the letter. “That's awful. I can't believe that,” said neighbour Yolanda Nykiforuk. Another resident Sharon Mayr said the writer should have sent it to the community management instead of the family. "Don’t send it to them. Let the condo board deal with them,” she said.

The brunt of the complaints laid out in the letter include “hooting and hollering” and “rollerblading and scootering on (neighbours’) driveways.”

“Your kids are extremely thoughtless and rude,” it reads. “We don’t like your kind around here, we lock our doors at night when there was no need to do that before you moved in.”

The writer claims that they complained to the condo board about the family multiple times. “It won’t stop until you’re gone,” they write.

Anderson and her husband have rented a unit in the community with their children for just 18 months.