Ashley Foster handed himself into police after CCTV footage featuring the two suspects wanted for the murder of Alan Greaves was broadcast on the news, the court heard.
Robert Smith QC, prosecuting, said he went to Ecclesfield Police Station with his mother and told officers he had witnessed the attack.
Mr Smith said that the night before Foster’s friend, Jamie Evers, had confronted him after seeing the news and asked if Bowling had something to do it.
Mr Smith said: “He told him Jono did it.
“Foster began to shake and looked as though he was going to be sick.
“Jamie asked him why he had done it and he said he didn’t know.
“He said he was scared and Bowling had threatened to kill him and his children and torture them if he said anything to the police.”
Foster declined to answer detectives’ questions, but submitted a written statement.
In it, he said: “On the day it happened he was going to smash someone else with a hammer. I had to stop him. I knew he was going to kill someone.”
He told police they saw Mr Greaves and Bowling quickened his pace before striking him on the head with the pickaxe handle with such force he fell over himself.
He claimed Bowling said to him: “That’s me being normal. Imagine me being sick.”
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