Todd is the 15-year-old who killed herself last week after suffering years of bullying. Many online memorial sites have popped up in response to her death, and thousands of people have posted comments on them.
Christine Claveau was looking at a site when she saw what she thought was a particularly hateful anonymous post.
She said the comment read, "It's about time this bitch died."
Claveau said she tracked down the identity of the sender in Toronto and forwarded a note to his employer, the retail store Mr. Big and Tall.
The man was fired.
"We are deeply saddened by the loss of Amanda Todd," said Dave McGregor, president and CEO of Grafton-Fraser Inc. which operates the retail chain, in response to a query from CBC News.
"Out of respect for the family, I decided not to comment further on this situation beyond our statement that we took the action we felt to be appropriate. I will tell you that the individual in question is no longer employed with our company."
McGregor said the company's ethics are based on tolerance, respect and fair and honourable treatment of all individuals, internally, with customers and the population as a whole.
"We have zero tolerance for the mistreatment of others no matter what form it takes," he said. "We feel that the focus should remain on the issue at hand, which is bullying and how we work together to stop it. Our thoughts and prayers are with the Todd family."
Mixed reaction online
"I'm glad that they fired him and they took such a strong stance against bullying," said Claveau.
"But I just think that even having him reprimanded or having the embarrassment of his company knowing what he did is what I was aiming for, just to say … you know what you do in your pastime can affect who you are at work and your personal life too."
Claveau said she has received a lot of response to what happened — most of it positive but some of it negative.
"You can't please everybody, so I'm getting a lot of people saying I was the bully in the matter, or it wasn't right to contact his employer. So I'm getting a little bit of negative backlash."
Claveau said so-called "internet trolls" must be held accountable for what they say and do online.
"Trolls" are people who anonymously post negative comments on the internet to elicit a reaction.
She said she's more encouraged than ever now to monitor the internet and "out" those behind hateful statements.Claveau has started a group of concerned moms who plan to continue alerting authorities to cyberbullying taking place online.