Tassart's grandma said

Grandmother Marie Fitzgerald, 81, told Nine News she had been left "gobsmacked" anyone in her family could have been responsible for the worst massacre in New Zealand's modern history.

Describing Tarrant as a youngster, she said: "He spent most of his time on computers and learning the ins and outs of computers and playing games on computers."

She added: "I don't think girlfriends were on the agenda" - explaining that talking to girls was "too hard".

Speaking from her New South Wales home, the elderly woman said: "It's only since he travelled overseas I think that that boy has changed completely to the boy we knew."