Orange County District Attorney Todd Spitzer said the couple had finished shopping and were waiting for a ride when two men in masks jumped out of a white Toyota Camry.
They put a gun to Doug McKay’s head, forced him to the ground and demanded his watch, Spitzer say.
One of the men then attacked Patricia McKay, throwing her to the ground and dragging her into the street, into the path of the getaway car, which was being driven by a third man.
“McKay’s husband jumped in front of the vehicle trying to stop his wife from being run over.”
Spitzer said the driver - identified as Leroy Ernest Joseph McCrary, 26, of Los Angeles - accelerated, pushing Doug McKay out of the way.
He ran over Patricia McKay and dragged her body about 20 metres.
Local man Beau Bayless tackled one of the robbers - identified as Jayden Cunningham, 18, of Lancaster - but was shot at from the getaway car by 18-year-old Malachi Eddward Darnell, of Los Angeles, Spitzer said.
Bayless previously told RNZ he heard a “crack” and the sound of the bullet as it “whistled past both of our heads.
“I saw his buddy out the passenger side, gun pointed at me, and he fired two more at me and I hit the deck. I had to let the guy go.”
Cunningham was arrested after “bailing out of the vehicle” and McCray and Darnell were arrested after a police chase, Spitzer said.
The trio had been charged with special circumstances murder and were being held without bail.
The charge included the felony enhancement of causing the death of an elder over 65.
McCrary had also been charged with one felony count of attempted second-degree robbery, and one felony count of evading while driving recklessly.
Darnell had been charged with one felony count of second-degree attempted robbery, one felony count of attempted murder, one felony enhancement of personal use of a firearm and one felony enhancement of personal discharge of a firearm.
Cunningham had been charged with one felony count of attempted second-degree robbery.
“Our entire community extends its deepest sympathies to the loved ones of Patricia McKay and to the entire country of New Zealand as we mourn her senseless death in the commission of a crime that should have never happened.”
In a statement issued on Saturday, McKay family spokesperson Nick Hern said the family wanted to express their “deep gratitude” for the support they had received since McKay’s death.
“In particular, teams from the Ministry of Foreign Affairs, the New Zealand Embassy in Washington and the office of Consulate General in Los Angeles have been extraordinary in the work they are doing helping our family, including liaising with state and federal authorities in the US.
“Thanks to this heartfelt and expert support, along with the excellent work of all the US authorities including the team from Orange County, and especially Newport Beach Mayor Will O’Neill, great progress is being made to return Trish to New Zealand and we hope to have her home within the next week.
“Once her return is confirmed we’ll advise of plans for Trish’s farewell.”