This immediately indicated to him the driver had run over somebody or something, the inquest heard.
Mr Primmer drove up to what he thought was a rubbish bag but realised it was a body in the middle of the road when he was about two metres from him.
He backed his vehicle up and put his hazard lights on so others would not run over Mr Hoskins.
"I got out and looked at him then I noticed the blood," he said.
"I looked up and saw the other car about 100 metres ahead ... the vehicle took off shortly afterwards - he would have seen my hazard lights go on.
"When he took off he bloody had his foot down, he was in a hurry."
Mr Primmer said Mr Hoskins was lying in the foetal position in the middle of the road and the soles of his shoes had been torn off, suggesting he may have been dragged.
Blood poured from a head wound and from his mouth. Mr Hoskins was unresponsive but continued banging his head on the road as he gasped for breath.
The inquest earlier heard from Malcolm McMartin who met Mr Hoskins at the wedding.
He said Mr Hoskins was "boisterous" but not annoying anyone. He had been drinking "an everything drink" - emptying unused drinks into a plastic pitcher.
Mr McMartin said he went to bed about 4am and Mr Hoskins was "still coherent and making sense" when he left him.
David Gregory Mascelle, who will give evidence to the inquest tomorrow, handed himself into police on January 16 - more than 24 hours after the incident.
The 48-year-old was charged with careless driving causing death when he appeared in Hamilton District Court but police dropped the charge about six months later.
Mr Mascelle's wife Ngaire - a community magistrate - was a passenger in the car on the night Mr Hoskins was run down.
She was removed from the community magistrate roster while her husband was before the court.
Coroner Garry Evans said the court was required by law to examine all aspects of Mr Hoskin's death, including how he came to be on the road at 4.30am and whether the driver had seen and adequately identified him before running over him.
The inquest held at the Hamilton District Court is set down for two days with a further eight witnesses to be called.