A taxi driver gunned down by Derrick Bird had "bragged" about slashing the tyres on the killer's car, an inquest heard today.
Darren Rewcastle, 43, was overheard saying he had "done" the tyres on Bird's Citroen Picasso.
Stephen Brew, a fellow taxi driver and friend of Bird, said the gunman complained that replacing them was costing him more than he was making on the job.
Bird named Mr Rewcastle as responsible, pleading to his friend: "What am I to do?"
Mr Brew told the hearing: "I have heard Darren saying it to other people on the rank, that he had darted Birdy's tyres."
After the cold-blooded murder of his twin David and solicitor Kevin Commons, 60, Bird drove to the taxi rank in Whitehaven where he and Mr Rewcastle both worked.
He called the victim over to his cab and blasted him twice with a shotgun in the face and stomach.
Bird, 52, went on to injure three other taxi drivers in the town, killing 12 people before turning the gun on himself on June 2 last year.
Mr Brew told the inquest into the deaths that he often chatted with Bird when they both worked as cabbies.
He described Bird as a "nice guy, very quiet" but added: "He would bottle stuff up."
The inquest, now in its fourth day, has heard a number of reasons why Bird may have gone on the shooting spree.
He was convinced he was going to jail for not paying enough tax and thought his brother and solicitor Mr Commons had "stitched him up" over the matter.
The hearing at the Energus centre in Workington, Cumbria, has been told that Bird was also worried about his elderly mother's ill-health.
And Bird was also bullied and taunted by a "clique" of other taxi drivers in Whitehaven, the inquest has heard, prompting him to warn: "They are going to get it big style."
Bird had the tyres on his car punctured with a sharp dart on five occasions, among other damage.
Mr Brew said once he helped his friend change his punctured tyres.
"Did he say who he thought was responsible?" coroner David Roberts asked.
"Yes," Mr Brew replied. "He said Darren was bragging that he had done his tyres. It was open knowledge on the rank.
"I have heard Darren saying it to other people on the rank, that he had darted Birdy's tyres."
Bird later asked his friend: "What am I to do?"
"I said 'What about?'. He said 'Darren'. I could not give him an answer," Mr Brew said.
"He was asking what he could do, how he could resolve the matter."
Mr Brew said Bird also had his car radiator punctured with a screwdriver, saying: "They have been at my car again."
The witness said Bird complained that his brother David did not pull his weight in looking after their frail mother and he was left "doing everything" to help her.
Earlier, the hearing was told one reason why Bird might have been targeted.
Female driver Donna Grierson said she had been assaulted by a passenger, whom Bird later picked up on a fare, sparking the reaction by fellow taxi driver Mr Rewcastle.
The inquest, expected to last four weeks, is also investigating the deaths of Bird's other victims: Susan Hughes, 57, Kenneth Fishburn, 71, Isaac Dixon, 65, Jennifer Jackson, 68, and her husband James, 67, Garry Purdham, 31, Jamie Clark, 23, Michael Pike, 64, Jane Robinson, 66, and Bird himself.
Ron Pattinson told the hearing how he discovered David Bird at the victim's home in Lamplugh.
He found his neighbour's semi-naked body wearing only a T-shirt, bloodied and lying dead in the foetal position in the doorway of the bedroom.
In the early hours of June 2, Bird had entered his twin's home, High Trees, a traditional, 300-year-old farmhouse, before blasting his brother 11 times in his neck, face, head and back.
There were signs of a struggle: a television had been knocked over and the bedroom door, which had a bullet hole through it, was partially ripped off its hinges.
Blood was all over the walls, the TV, the door frame and the landing.
Mr Pattinson said he discovered the body of the father-of-three at about 10.45am.
He had been alerted by Timothy Shields, who called round to the house after Mr Bird had failed to turn up for work.
Mr Pattinson and his wife Jennifer went to investigate, entered through the front door, normally left unlocked, and went upstairs.
"He was actually lying just inside the doorway, almost touching the door," Mr Pattinson said.
"He was in the foetal position with his back to the door.
"There was a fair amount of blood around and under David's body."
The neighbour said there were no signs of life and rigor mortis had begun to set in.
Mr Pattinson said it was obviously an "unnatural" death and an ambulance and police were called.
By now Bird was on his shooting spree, and when paramedics arrived Mr Pattinson said they were "stressed" and it became clear "something was going on elsewhere".
The witness added: "We were told there was a lock-down, to go into the house and stay put and do nothing else."
Kerrie Evans told the hearing that she knew Mr Commons "extremely well" and described their relationship at the time of his death as "intimate".
He sent her a final text message, timed at 10.04am on June 2, nine minutes before the first 999 call was made to report the shooting of Mr Commons, timed at 10.13am.
"It was just a kiss," Miss Evans told the inquest.
She recalled a conversation the day before when David Bird had called at Mr Commons' farmhouse to escape Derrick's attention.
While there, David told of "endless" telephone calls from his brother, who repeatedly turned up at his house.
Mr Commons suggested David should take his brother to hospital.
David "smirked" and replied: "Maybe I should", Miss Evans said.
Susan Rooney, whose garden overlooked Mr Commons' driveway, told the inquest she saw part of the gun attack.
Mrs Rooney said she heard a shot and saw Mr Commons staggering back up his drive, pursued by another man, and she called 999 to report what she thought was an air-rifle incident.
John Dunn, a neighbour, was alerted and went to the farmhouse to investigate.
He saw a body sprawled on the ground.
"I could see this person had a lot of blood coming from his head and it had been running down the drive towards me," he said.
In a statement, Andrew Benn, a local farmer, said he had known Bird for 35 years and they would drink in the same pubs.
Mr Benn said there would be "banter" and he himself would get stick about his ginger hair.
"Derrick was not the best-looking person in the world, so he would get stick about this. He would never retaliate. He would maybe go quiet for a while."
Mr Benn saw Bird in his car on the morning of June 2, driving away from Mr Commons' farmhouse.
"I waved at him and said 'All right, David?'. He kind of acknowledged me in that he moved his head to one side.
"I would describe him as looking a bit wild. He was white-faced and stary-eyed - almost a vacant expression."
The jury was then shown photos and CCTV from the crime scene.
It showed Mr Commons' body lying on the ground from a distance.
He had been blasted with the shotgun in the shoulder and shot twice in the head with the .22 rifle.