His mother told the Herald she is devastated her only contact with her son may now be jeopardised because of the mail he has received while behind bars.
This week the accused gunman's handwritten six-page letter to Russia appeared on the website 4chan - a notorious online chat room for right-wing fans to post their views.
Corrections Minister Kelvin Davis confirmed there was more than one letter. It was later revealed the accused had tried to send nine letters while in solitary confinement, two of which were withheld.
But he managed to send two to his mother and five to unknown recipients.
Sharon Tarrant said writing to her son was sacred to her.
"Other people with their own agendas are making it difficult for us to maintain contact with him. Like 4chan - it's about their ego. How dare they? They have taken away the right from me to hear from my son."
She believes her son started "unravelling" after her former husband Rodney died of cancer aged 49, in 2010. Tarrant became withdrawn and sought solace in gaming, she said.
"He suffered from anxiety and chronic depression from his father's death.
"It was the space he slipped into when he was grieving. All of those people on the dark web encourage each other, it's so frightening. But what they don't realise is they are chronically depressed."
Schoolteacher Sharon Tarrant said she pleaded and argued with her son to take a different path away from gaming and away from the "dystopian sorts", but he was already hooked.
"Gaming is addictive because everyone is a winner. You are not learning about the real world where things don't always go the way you want it.
"You have to work hard and communicate with each other but young people have lost that ability and go into spaces that are psychologically harmful. It's horrendous, I see it all the time as a teacher."
Sharon Tarrant says she and her family have been targeted since her son's arrest, with people coming to the family home in New South Wales and harassing and abusing her and her partner.
It happens again after every other attack where people draw links to the Christchurch mosque shootings - such as the Poway synagogue shooting on April 27 in California and the Walmart shooting on August 3 in El Paso, Texas, when 22 people died and 24 were injured.
Sharon Tarrant wants the public to know she will always love her son.
She says that as his mother, nothing he is alleged to have done is right, "but every week I wonder if he's still going to be alive".
Corrections chief executive Christine Stevenson apologised yesterday for allowing the letter to be sent, saying the accused gunman would be blocked from sending or receiving mail pending a review.
"I would like to apologise for the distress that this has caused to those impacted by the tragic events of 15 March," she said.
"We have taken swift action to ensure that our processes are as effective as we need them to be. With immediate effect, this prisoner will not be able to send or receive any mail until we have absolute assurance that the process in place for screening and assessing his correspondence upholds the safety of the public, both in New Zealand and internationally."
Revelations about the letter have opened fresh wounds for victims of the twin mosque attacks, retraumatising those who were injured or had lost loved ones.
Survivor Nour Tavis told the Herald he was angry and upset to hear about the prison letters.
"I think it's not a good idea that he can send them, he's going to spread hatred.
"The words might appear like they are innocent but they are dangerous - they could have codes... people like him could be reading between the lines, there could be a message.
"I call him a contaminant and what he is doing is contaminating others."
Davis confirmed the accused gunman had received a "couple of dozen" letters from around the world while behind bars at Auckland Prison.
He said Corrections had made a mistake in allowing one of Tarrant's letters to be sent, which found its way online.
"I've expressed my disappointment to them. They have apologised to me, but more importantly for the distress it's caused to a large sector of our community.
"They need to own it, they need to make sure it doesn't happen again."
Prime Minister Jacinda Ardern said it was wrong for the accused man to have been able to spread his "hateful views".
