The fact by-standers were able to help victims in the Dunedin knife attack, show why knowing first aid is so important

First aid experts say it's a wake-up call for all of us.

Four people were stabbed at Countdown Dunedin Central on Monday afternoon - each is recovering from surgery in Dunedin Hospital.

First Training director Mark Judge says New Zealanders are good at not walking on by, but rather stopping to help out.

He says knowing what to do can help save someone in the first minutes of life-threatening injuries.