A police officer punched and slapped an elderly motorist leaving the pensioner with a fractured jaw before fleeing the scene.
PC Stuart Box attacked Peter Burgum, 70, who passed away weeks later from unrelated causes.
The victim's wife, Caroline, was also injured in the attack and said her memories of her late husband are 'indelibly marked' by what happened.
The incident unfolded after Mr Burgum overtook the cycling off-duty officer, then 44, in Gloucestershire in April last year, a misconduct hearing was told.
PC Stuart Box attacked Peter Burgum (pictured) who passed away weeks later from unrelated causes.
Box banged on the side of Mr Burgum's Mitsubishi estate after he braked, and hit his wing mirror.
Box screamed at Mr Burgum, calling him 'a stupid b*****d' who 'nearly f*****g killed me'.
He then slapped Mr Burgum, who took out his phone to film the incident as he backed away.
The former officer later claimed he had been hit first as he grabbed the phone and threw it over a fence, before punching the victim.
When Mr Burgum fell to the ground his wife shouted: 'You've killed him', the misconduct panel heard.
Despite her attempts to stop him, Box got on his bike and rode off without calling 999 or leaving his details.
Mr Burgum suffered two fractures to his jaw, requiring surgery that left him unable to eat solid foods as well as cuts and bruises.
A misconduct hearing held by Avon and Somerset Constabulary yesterday found Mr Box would have been sacked for gross misconduct if he had not already resigned.
The force said it had investigated the incident and presented its evidence to the CPS, which decided that no criminal charges should be brought.
Box has also been banned from the police for life.
Elliot Gold, representing Avon and Somerset Constabulary, said the officer was