First Person - On Deans Avenue I watch a silver 4WD cruise along. A police car is nearby. It doesn't take much around here for the imagination to run wild.
My darting eyes search the front gardens of homes and the fences I would leap over if it happened again.
If it happened again.
It occurs to me that local migrants must be thinking the same thing every day, stricken by fear. They don't need my imagination; they have their own scarred memories.
Ten years ago I was living in Sydney with an Australian-born Indian medical student. He loves his cricket and sounds more Aussie than Richie Benaud.
After news broke of Indian taxi drivers and students being targeted in violent attacks in Melbourne, he told me he was walking down the road and heard someone running up behind him, paralysing him with fear.
When he turned around he saw a harmless jogger about to pass by.
A very able-bodied male Aussie, in his own country, paranoid about his skin colour triggering racists after some Indian guys were bashed in another state.
If you are not Muslim, try to imagine Muslims in New Zealand now - use that imagination. Would you leave your headscarf at home?
You just might, just in case it was to happen again.
There's silence and some sad, understanding smiles outside the Al Noor Mosque on Deans Avenue. A police officer holding a serious weapon chats candidly with some children while she explains her work shifts.
Another officer at Linwood Avenue tells me the shifts were 12 hours to begin with, and now they are back to eight, but he hasn't had a day off in the last week and a bit.
He is sick of it and wants to go home. Or do something else. But he could be here for weeks.
Just in case it happens again.
And the prime minister has announced a commission of inquiry - looking at the police, customs, immigration, the GCSB and the NZSIS - because none of them knew the attacker.
They don't want to miss anyone else, or it could happen again.
The guns laws will change because someone sold him the guns online, because he had a clean record, and everyone is worried there could be others like him out there.
Flowers are already dead and droopy in Hagley Park, and the candles have burnt out, and the dust from dry March days sticks to the banners and flags draped around trees.
A slightly careless driver parks his car on the side of Deans Ave, and hits the kerb, causing a loud, sharp, scraping sound and everyone pausing for thought at the gates of the mosque jump and turn.
White people in shorts and jandals - neighbours perhaps - they are also on edge. The driver slowly holds his hand up to apologise.
Turn that imagination back on again and think of the Muslim. Every unexpected sound is a threat.
Some have fled war zones, where every day is a collection of false jumps, because every month there's a real one.
They came here because they didn't want it to happen again.
I walk past the laneway next to the mosque, where the terrorist parked his car. A police officer stands guard. It was just the other day.
Among every evil thing inside that car, the terrorist was in possession of a black, reusable, biodegradable tote bag, with "Kiwi As" written on it: a sickening message for native-born Kiwis, a frightening one for a migrant.
While grave mounds are still so fresh, it seems far far too early to worry about a reputation being shot - and despite what has happened, Muslims are gathering and returning to their mosques, to pray. They trust the New Zealand authorities and are thankful.
They all keep saying that their brothers and sisters who died are in a better place. They are shahid: martyrs or witnesses.
They want to go there too one day.
No matter how safe we honourably try to make it, that's the only place where it can never, ever, happen again.