A security studies and counter-terrorism expert says it's unlikely anyone could have seen the Christchurch terror attack coming.
The country remains at its highest security threat level in history after a gunman opened fire in Christchurch, killing 50 and wounding at least 50 others.
Dr John Battersby told Kate Hawkesby alarm bells are only ringing in the wake of the devastation.
"We lived in a country where nothing like this had ever happened, so it's a big call to point the finger and say; 'this person is going to do something'," he said.
"I'm pretty sure security services in New Zealand have intervened with people who were on this tack. but id they have intervened and succeeded, we will never know and they will never know how successful they were because the outcome isn't there to prove it.
He said there are a number of reasons why it was so hard to see this attack coming.
"He managed to keep a pretty tight lid on exactly what he was intending to do."
"He has managed to get himself firearms licenses, so he has gone and got people who have supported his character and the decision has been made that he's a 'fit and proper person'."
"There are plenty of comments from people who worked with him and never saw any signs of this extremism. This man has no criminal history. He has travelled around different parts of the world like a lot of us have."
Battersby said it's easy to see an issue in hindsight.
"When we look back we can see things much clearer. It's quite clear by this outcome somebody should have seen him."
"It's becoming more and more evident that there were risk factors around him."
He said it's legitimate to be wondering how he was missed but it is unlikely someone like this will be missed again.