A man was battered to death with a bike lock after a row in an east London chicken shop, a court has heard.
Catering manager Zdenek Makar was left dying in the street after he was attacked while on his way home in Poplar on 21 September.
The Old Bailey heard Raymond Sculley struck the 31 year old in the head with the heavy chain, then hit him twice more while he lay on the ground.
Mr Sculley, 29, of Tower Hamlets, denies murder.
The jury heard Mr Sculley, a painter and decorator, had spent the evening playing video games, smoking cannabis and chatting with friends.
He came across Czech-born Mr Makar, who was coming home after a night out, having cycled with his friends to a chicken shop in East India Dock Road.
Prosecutor Lisa Wilding QC told how Mr Makar allegedly joked to one of the group: "What's this? A bike gang?"
CCTV footage showed Mr Sculley then acting aggressively towards the hospitality manager when a row broke out.
He then followed the 31 year old as he left, "removed a bicycle lock... and approached the helpless Mr Makar", Ms Wilding said.
She said the chain struck Mr Makar to the left side of his head, catching him behind the ear and knocking him to the ground, where he was hit again.
Mr Sculley then allegedly stood over the dying man and said "look what you made me do", before departing.
The court heard the attack ruptured Mr Makar's blood vessels and he suffered acute bleeding.
The jury were told that Mr Sculley contacted one of his friends who saw the attack and told him he had "messed up".
Two days later he handed himself into police saying he was "shocked...like I've destroyed potential lives and future careers."
The trial continues.