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.