Michael Mullen claims he innocently became gunman Michael McDougall's getaway driver following the murder of Tipu Sultan after agreeing to run a simple errand on his motorbike.
The 25-year-old mechanic told Newcastle Crown Court he had been asked to take McDougall to Smilers newsagents to buy cigarettes that night but was told to stop the bike outside Mr Sultan's Herbs & Spice takeaway in South Shields.
Mullen said he heard a "bang" during the moments McDougall was off the bike before he was told to drive on.
Mr Sultan, 32, of Sunderland, died from a shotgun wound to the neck as he cleaned the kitchen at his shop on April 7 last year, with his father and the chef they employed.
Campaigners rally against Local Plan after farmland in Cleadon earmarked for 156 homes
Appeal to find owner of lost Labrador after dog found near Jarrow Cemetery
Pair set up cannabis farm in town centre flat
South Shields man jailed for terrifying physical and sexual assault on woman in her own home
Mullen refused to answer detectives' questions after his arrest but named McDougall, who he said he is now "frightened" of, in his defence statement as his case was prepared for trial.
From the witness box, Mullen told jurors: "If I say nothing I run the risk of losing my son.
"If I say something I run the risk of losing my life.
"As soon as I handed my defence statement in there was immediate threats made upon my life. I am being held in solitary now."
McDougall, 47, told jurors yesterday he was not at the takeaway and had no involvement in the shooting of Mr Sultan.
Mullen told the court today McDougall confessed to him Mr Sultan's death was during a "robbery gone wrong" to pay a £750 bailiff bill.
Mullen, who has previous convictions, claimed he was asked by McDougall to take him for cigarettes that night and was directed to the rear of the Herbs & Spice shop.
He said in evidence: "He told me to stop and stepped off and said he would be five minutes.
"While I was there I heard a bang. I thought nothing of it at the time because a group of kids came running past me.
"I thought it was just the kids messing about.
"After that, Mr McDougall got on the back of the bike and said 'howay, go on then'."
Mullen said it was only after they both got off the bike his girlfriend's house he realised McDougall had the gun.
He told the court: "At this point I saw McDougall, standing there with a sawn-off shotgun."
Mullen said he only realised something serious had happened at the shops when he spoke to his girlfriend at the house.
He said: "She was telling me she knew what had just happened, it was all over Facebook.
"She told me someone had been shot near Lake Avenue.
"I told her McDougall was in the back garden with a shotgun."
Mullen said he was scared and his girlfriend was "hysterical" at the house.
He said McDougall disposed of the weapon in bushes and the pair went their separate ways after leaving the house but met up again later.
He told the court: "I asked him if it was him involved in the shooting. He went on to say it was a robbery gone wrong.
"I asked him whey he intended on robbing this bloke and he said because bailiffs had been at his house that day to collect £750 and that was it.
McDougall, of Hylton Avenue, and Mullen, of Hawthorne Avenue, both South Shields, both deny murder, manslaughter and possessing a firearm.
McDougall denies an additional charge of possession of a firearm and Mullen denies perverting the course of justice.
The trial continues.