A letter sent to the grandmother of a 13-year-old boy with autism in Newcastle, Ont., does not constitute a hate crime, police say, but authorities are continuing to treat it as a criminal investigation.

In the letter, the author complained the boy scared her "normal children" due to the noises he made while outside, and said that his family should "do the right thing and move or euthanize him."

The typed, one-page letter has prompted outrage, with many rallying around Brenda Millson’s family. But Durham Regional Police say the wording is not enough to be considered a hate crime.

"Despite the hateful language used … the content of the letter falls below the threshold for a hate crime," police said in a statement Tuesday. "However, there are other Criminal Code issues that are being considered."

Millson said she immediately contacted police after receiving the letter. Her grandson Max Begley, who was diagnosed with autism as a toddler, lives with his parents and older brother in nearby Oshawa, Ont., but he had been visiting her home.

The letter states that Max "is a hindrance to everyone and will always be that way." It goes on to say that "they should take whatever non-retarded body parts he possesses and donate it to science."

"At first I couldn't believe what I was reading," Millson said, adding that she was shaking in disbelief. "It's just so sick."

Despite the police conclusion that the letter does not constitute a hate crime, Millson said she still considers it to be a “hate letter.”

Since news of the letter first surfaced, there has been a huge outpouring of support for the family from neighbours and the autism community.

On Sunday, at least 120 people waited outside Millson's home to show their support.

One neighbour said this sort of behaviour is unacceptable.

"Whoever wrote this letter can just … they can leave, they can go live in the wild with their normal children, as far as I am concerned," neighbour Julie Smith said.

According to the family, the only hostility they had previously received happened four years ago when one of Max's balls was returned cut up with scissors.

"Whoever wrote it is a disgusting human being," Max's father James Begley said.

A criminal investigation is underway and police are asking anyone with information regarding the case call Crime Stoppers at 1-800-222-8477

With report from CTV Toronto's Calvin To and files from The Canadian Press