Fifty people died on Friday after a gunman carried out shootings in two mosques on Deans Ave and Linwood Ave.
Australian man Brenton Tarrant has been charged with murder for allegedly carrying out the attack.
The AM Show Australian correspondent Jason Morrison said Australians are in a state of shock over the attack.
"All I guess we can say is overwhelmingly we are so so so deeply sorry."
Mr Morrison said there is some culpability in Australia because Tarrant wasn't on any watchlist or being looked at.
Tarrant will go down as a mark against the history of both countries, Morrison said.
"He will go forever in the history of both of our nations as a black mark and we hope one that will be resolved."
Most people are simply reacting in disbelief.
"Disbelief would be possibly the simplest and most useless thing you really can say, utter disbelief."