Parminder Sanghera, 25, of Wolverhampton, who drove Quinn away from the scene of the stabbing and was also caught on CCTV wielding a machete, was found guilty of manslaughter.
Senior Investigating Officer, detective chief inspector Ally White, said: “This was a sustained attack on an innocent man who was heard by eye-witnesses to protest repeatedly to Mr Quinn that he’d got the wrong person. Despite this Mr Quinn not only stabbed him once, but then chased him and stabbed him again.
“Daniel Fitzjohn was by all accounts, a very decent, mild-mannered man with no history of involvement with the police or with drugs. He was simply caught in the wrong place at the wrong time by a drug dealer who stabbed him to death in a fit of anger.
“I am very pleased that we have managed to get justice for Mr Fitzjohn and his family and I would like to take this opportunity to commend them all for the bravery they have shown throughout the trial – the things they have seen and heard, including the moment Daniel was stabbed will have left a mark that will never fade.”
During the trial, the jury heard how the trouble started with a scuffle outside the Fairfield News shop in Kingsley between Quinn and a customer who regularly bought drugs off him.
But Mr Fitzjohn - who had never taken drugs in his life and had met the customer that evening on a trip to the pub - saw Quinn go to hit the man with a large branch and intervened to punch him to the floor.
That should have been the end of it - but instead, Quinn collected Sanghera from a nearby house, armed the pair with a machete and a knife, and went out to 'hunt down' Mr Fitzjohn and his friends.
When they found them in Brookfield Road, Sanghera led the charge with the machete and the pair ran at them.
In the foot chase that followed across Kingsley, Mr Fitzjohn was separated from his friends.
When Quinn caught up to him, he stabbed the 34-year-old twice before escaping in a grey Mini driven by Sanghera.
Members of the public rushed to help Mr Fitzjohn, but sadly, he died in hospital less than half an hour later.
Mr Quinn then went on the run from police, hiding out in Wales for a few days. But police were closing in and on 19 June, 2018, he handed himself in and was subsequently charged with murder. Mr Sanghera handed himself in on June 25 2018.
In court, Quinn even claimed he stabbed Mr Fitzjohn out of 'self-defence' when he thought he was going to swing a beer can at him. Prosecutor Mary Loram QC called this 'a blinding lie'.
Quinn and Sanghera are due to be sentenced at Northampton Crown Court on Thursday, February 21.