The man who carried out Friday's attack is being described as a ticking time bomb.

Sri Lankan Ahamed Aathil Mohamed Samsudeen was shot dead by police at New Lynn Countdown, after he stabbed at least five people, and two others were hurt.

Herald reporter Sam Hurley has followed Samsudeen through the courts and says he seemed like a scary man to be let out into the community.

He says everyone knew he'd eventually be released from prison and there was a sense this event was an inevitability.

Otago University law Professor Andrew Geddis says under the existing law nothing else could've been done to detain the terrorist.

He says the prosecution and police went above and what they'd usually do, in an attempt to keep him behind bars.

Geddis says that includes asking the High Court to apply the Terrorism Suppression Act in a completely novel way, which didn't have much of a show.

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