Police would not discuss the post mortem yesterday.
Mr Henderson said at first he did not realise the charred remains were human.
"It's just one of those places you drive through. Being a mechanic I am nosy, so I decided to stop and take a look. I noticed it was a Subaru because of the roof shape. I noticed there was something in the driver's seat.
"I walked toward the car. I thought someone had put a dead sheep in there to be funny.
"Everything except for the car shell was incinerated. The front number plate was on the vehicle."
Mr Henderson, who is a member of the North Canterbury 4WD Club, has lived in Rangiora for seven years and said the riverbed was his "local playground".
"I always drive along that track. The police interviewed my brother and I," he said.
"I wished we had kept on driving because it was a grisly find. It really weirded me out. It's not unusual to see burnt out vehicles near the area. I've been driving along this track for about seven years and I've seen eight burnt out cars.
"It's going to take me a while to get over this."
Police are this morning refusing to say whether Mr Bell's mysterious death is still being treated as a possible homicide.
"At this stage the inquiry remains a suspicious death investigation," inquiry head Detective Senior Sergeant Brian Archer said yesterday.
"We are trying to put together a picture of Mr Bell's movements in the days leading up to his death.
"A key component to this investigation is determining when the car was burnt out. We now believe this was prior to Thursday evening. A member of the public who was in the area has come forward and indicated they had seen the burnt out shell of the car at around 4 to 5pm on Thursday."
Mr Bell was last seen at his Dallington home on Thursday morning.
Detective Senior Sergeant Archer said police were still making inquiries into Mr Bell's background for clues to his death.
He was a self- employed car salesman, who bought cars off Trade Me, repaired them and re-sold them.
Bullet holes found in the side of the car were not related to Mr Bell's death, or the fire.
"A group of recreational shooters came forward and told police they were in the vicinity on Friday evening. They have indicated that the car was already burnt out at that time and they fired shots at the vehicle using a rifle."
Police have spoken to Mr Bell's family and partner who were "extremely upset and are trying to come to terms with his death".
Anyone with information about Mr Bell or the 1989 silver Subaru station wagon is asked to contact police on 03 363 7400 or Crimestoppers 0800 555 111.
