While there are countless stories of tragedy emerging from Christchurch, there are also many of heroic bravery.

In particular, the two officers who took to the streets hunting the alleged gunman before taking him down on the footpath.

It's unlikely the person who filmed it knew exactly what was happening, but video shows armed police wrestling a man to the ground in broad daylight on the side of the road.

The world now knows it was the man accused of the Christchurch killings.

The officers who tracked him down are being described as "heroic".

"Those two police officers acted with absolute courage," Police Commissioner Mike Bush told media. "I am so proud of what they've done."

We now know more about exactly what happened in the moments before, including the fact that the officers were at a training day, preparing for an event like Friday's tragedy.

Police Association President Chris Cahill called it a "hell of a coincidence".

"It points out the value of training."

It's reported the officers were training on an unused floor at Princess Margaret Hospital on Friday morning. When the shooting began they were still there, but had firearms and patrol cars parked outside.

They set out to find the gunman immediately, who had already fired on the mosques in Riccarton, and Linwood. Minutes later they saw a suspicious car on Brougham Street and rammed it off the road.

"They've just said 'We've got to take this person out', they've put aside their own risks," Cahill says.

It's reported the officers noticed a cache of weapons in the boot.

Bush says they're "overwhelmed and humbled" by the nation's positive feedback to the video.

"If you ask them, they will tell you they were just doing their job."

A job police say saved more lives from being taken.

Both officers have now been stood down, and one has taken leave but is expected to be back on duty soon.

Newshub.