Peter John Carroll used a steering wheel lock to hit Marcus Luke Tucker several times, in an effort to "calm" him down.
"I picked up the steering wheel lock and hit him in the shoulder...I hit him again in the shoulder, he went floppy and stopped moving," Carroll told the High Court at Christchurch today.
Carroll, 53, is on trial for murder after the body of Tucker, 36, was found bashed and burnt near Lake Ellesmere on Anzac Day last year.
The trial began last Monday, when the jury heard that Tucker and Carroll were both involved in the city's drug scene, and Tucker had allegedly been using fake $100 notes to buy drugs days before his death.
The court heard that an associate of Carroll's, whose name is suppressed, was selling drugs for him and had received fake $100 notes from Tucker during a drug deal.
Carroll realised he had been scammed when he went to collect the money from his associate.
Carroll told the court he started counting the money and the top three notes were real, but the rest were photocopied.
On April 24, Carroll went to his associate's house and found Tucker asleep in a bedroom.
Carroll said, "I'm here, I'll sort it out now".
Carroll told the court he hit Tucker in an effort to intimidate him, but Tucker kept struggling and would not calm down.
Carroll said he must have hit Tucker in the head, because he was knocked out and saw "quite a lot of blood" on the floor underneath Tucker's head.
After realising Tucker was not breathing, he went outside for a cigarette and told his associate that he thought he had killed Tucker.
The court heard that Carroll, along with a man, whose name has been suppressed, drove to a road near Lake Ellesmere, where they burned Tucker's body.
Carroll was arrested six days after Tucker's body was found.
The trial will continue on Wednesday.