No one knows the value of blood more than Napier police officer Bruce Miller.
Just over three years ago he was losing it.
Senior Constable Miller and his two colleagues, Len Snee and Grant Diver, were gunned down by Jan Molenaar after going to his Chaucer Rd house to execute a search warrant on suspicion of drugs.
Mr Snee died at the scene, while Mr Diver and Mr Miller took body shots from the gunman's high-powered rifle and staggered out on to the road.
"You just didn't expect something like that to happen," he said.
Stunned by the violence which erupted so quickly, he knew he was in trouble.
He was losing blood, but the terrible injuries he took were mainly internal after being shot in the lower back.
He could see that Mr Diver was losing a lot of blood, too.
"He ended up losing, and later getting a hell of a lot more blood than me."
Mr Diver was shot through the arm and groin.
It was the "amazing" treatment he received from medical staff, and the realisation that someone's donated blood had helped save his and Mr Diver's life that led to Mr Miller pledging his support for World Blood Donor day tomorrow .
"I had been conscious all the way out to hospital," he said.
"The hospital people were brilliant. They cleared everything for us after they were told what had happened and the whole care thing was just amazing."
He said the full magnitude of what was happening hit him as he was losing consciousness as he was being worked on.
"I didn't know if I'd come back."
Mr Miller was equally full of praise for the people the Blood Service are calling "modern day heroes" - "ordinary Kiwis who give blood".
"Something like that - it just showed you may need blood one day at short notice," Mr Miller said.
Mr Diver, a police dog handler, had also pledged his support for World Blood Donor Day but was unable to call and meet some of the Napier Blood Service crew yesterday as he was busy training a new dog.
"Grant's good, he's doing fine," Mr Miller said, adding that "now and then" his body let him know it had taken a serious blow.
"I still get twinges. It's in the ribs."
The officers were both contacted a couple of weeks ago by the Blood Service, through the Police Association's local representative Detective Sergeant Emmett Lynch, and asked if they would pledge support for donor day.
"I had no problems saying yes," Mr Miller said.
The New Zealand Blood Service's team leader in Napier Cathy Moriarty said she was delighted to get the officers aboard, with many police on the service's donor books.
"We are always looking for donors," she said.
"It is so crucial because there are so many people around the country who require this most valuable product - blood."
The Hawke's Bay service sought 120 units a week, but that was not always met. Donors, from age 16 upwards, only needed to devote between 45 minutes to an hour, once every 84 days.
"A simple gesture that has the power to save the lives of our loved ones."
To become a donor call the New Zealand Blood Service's Napier rooms on 834 1829.