A "river of blood" met the first paramedics on the scene of Christchurch's mosque massacres.

St John paramedics and 111 operators talked publicly about their experience for the first time on Monday.

Ambulance officer Paul Bennett said he was greeted with the most horrific scene he had ever witnessed when he arrived at the Masjid Al Noor mosque in Deans Ave on Friday.

"There was a river of blood coming out of the mosque and that's a scene that you don't forget."

The blood was "literally flowing off the terracotta tiles" and he was unable to get the stretcher past the bodies.

"I didn't go into the mosque because I couldn't get in ... because there were fatalities in the way. We ended up having to lift the bodies over top of other bodies on to our stretchers. Those people were bleeding and there was a lot of blood."

Bennett said he worked during the February 2011 earthquakes, but because that event was mother nature he was able to explain it in his head.

"The scene at Deans Ave was about hatred. That's the feeling I got from the Deans Ave site."

Karen Jackson, a paramedic who went into the Linwood mosque with members of the armed offenders squad, said there were bodies on the floor.

"The walking wounded were not there because everyone was already deceased or critical."

She had to step over bodies, and had trouble finding positions between the blood and the bodies to treat people.

Dawn Lucas, a 111 emergency medical dispatcher, said she realised the magnitude of the situation when she had one job on her screen and then blinked and there were another seven sitting there.

She ended up with 42 calls involving the shootings.

Jason Watson, an intensive care paramedic and shift supervisor, was outside the Deans Ave mosque directing ambulances and St John staff.

It was his job to bring a sense of calm to the chaos for incoming ambulance crews, he said.

"Initially there was chaos because that is the nature of it."

Watson limited the number of paramedics going into the mosque to about four or five because he did not want to expose too many staff to the horrific sight.

"A good half of the patients I saw go into the back of ambulances I expected to die within an hour and the fact that only one has is incredible and is a plus to the entire Christchurch emergency service community and the members of the public that helped out."

Watson paid tribute to St John staff because not only did they do an incredible job but they turned up to work the next day and were going to work tonight.

"That says a lot about the dedication of our people to this community."

Spencer Dennehy had been working as a 111 emergency dispatcher for just nine months when Friday's massacre happened.

She took a call from a woman desperate to get to her husband and 2-year-old child who were at the Linwood mosque.

"I was trying to tell her to stop because it was not safe for her to be there."

She later found out the woman's husband and child survived the shooting.

St John Christchurch territory manager Craig Downing said he had a significant amount of pride for his staff, who have already had to endure the earthquakes, the 2017 Port Hills fire, bus accidents and now the shootings.

All St John staff had access to an in-house psychologist and a management support team should they need ongoing help.

( Source: Stuff )