A man has been been sentenced to a whole-life prison term for murdering Met Police sergeant Matiu Ratana.
Ratana, 54, was shot in the chest and leg at Croydon custody centre by Louis De Zoysa, who had smuggled an antique gun into the building following his arrest on 25 September, 2020.
He was found guilty of murder, having claimed diminished responsibility.
Ratana's partner Su Bushby said her grief was "tormenting" and spoke of an "intense" feeling of emptiness.
De Zoysa, 26, of Banstead, Surrey, shot himself after the attack and was left with brain damage.
The defendant, who communicated in court using a whiteboard, remained impassive as the whole-life order was handed down.
Sentencing at Northampton Crown Court, Justice Jeremy Johnson said De Zoysa's autism and the impact on his family were not sufficient mitigating factors for a lesser term.
"You acted in cold blood. You intended to kill Sergeant Ratana. You aimed the gun at his chest at near point-blank range," he said.
"Even as he fell you re-aimed and fired a second shot at him. The aggravating factors outweigh the mitigating factors."
De Zoysa, who will serve his sentence at Belmarsh prison, becomes the 65th person in jail in England and Wales under a whole-life order.
During a three-week trial, the jury was shown video footage of the New Zealand-born sergeant being hit in the chest by the first of three shots discharged by De Zoysa.
A second bullet struck him in his thigh before De Zoysa was wrestled to the ground by other officers.
Ratana, who was known as Matt, died of his injuries in hospital.
In the hours before Ratana's death, De Zoysa was arrested while walking along London Road in Norbury, south London.
He told the two arresting officers he was carrying cannabis. However, in a holster hidden under his left arm he was also found to be carrying an antique Colt revolver.
His waistband was checked and he was frisked, but the officers missed the gun. They had no metal detector in their patrol car.
De Zoysa was then taken to Croydon custody centre in the back of a police van. Detectives believe it was during this journey he moved the gun from the holster to his hands, still cuffed behind his back.
There was also no metal detector at the entrance to the custody area, so the gun was not found as he entered. Once inside the custody suite, Ratana told De Zoysa he would need to be searched again.
As another officer pulled him to his feet, De Zoysa brought his still-cuffed hands from behind his back and shot Ratana in the heart.
'Nightmare continues'
Bushy told the court she had "lost her soulmate" and had been "in a state of limbo" ever since.
"I just sat there, waiting and willing him to walk through the door. I still do to this day," she said.
"I am hoping that one day it will get easier but at the moment the nightmare continues.
"At this moment in time, I cannot forgive him for what he has done; the person who shot Matt and ripped my life apart, my life as I once knew it."
The court also heard victim impact statements from other members of Ratana's family.
His sister Jessica Williams said: "The cruel and senseless actions of one man have left me and my family broken.
"The impact of what this person has done has left me shattered ... I feel like I could drown in the amount of grief I carry each day."
Ratana's brother James William Young said he had felt "hatred and anger" but "most of all pain and sorrow" since the shooting.
"The loss of my brother has been the hardest event in my life."
Met Commissioner Sir Mark Rowley described Ratana as an outstanding officer who "treated everyone with respect, with compassion and with good humour".
"Whether it was on the streets or in the custody centre, as a uniformed police officer, on the rugby field or later as a coach, it's clear that he was someone who made an enduring impact wherever he went."
- This story was originally published by the BBC.