A perception that George Taiaroa was lazy, and not doing his job properly, is thought to be the bizarre motive behind the road worker's murder.
Police are focusing on an accident about a week before Taiaroa was shot as the possible catalyst for the killing in south Waikato on March 19.
Taiaroa, 67, was shot in cold blood as he operated a stop-go sign at a single-lane bridge on Tram Rd in the Kinleith Forest near Atiamuri.
Police believe they know the motive, which they have said was "misguided", "beyond comprehension" and would appal most people.
Sources said the alleged motive relates to the incident a week before the murder.
A vehicle towing a trailer travelled through the Tram Rd roadworks, but the driver failed to see Taiaroa because he was sitting on the back of a flat-deck truck with his sign.
The driver kept going, but had to reverse when he encountered the roadworks. As he backed up, he collided with another vehicle that was following, causing damage to that vehicle.
It is understood the driver of the first vehicle became infuriated, blaming Taiaroa for the accident.
Taiaroa filled out an incident report, which included the names of the drivers involved and number plates.
He also told his colleagues what had happened at his next smoko break, but did not consider the incident anything more than minor.
It is understood police were able to track the drivers of both vehicles from the incident report.
The first vehicle was not a blue Jeep Cherokee, of the type seen leaving the scene of the murder a week later.
It is understood police do not believe the driver of the first vehicle shot Taiaroa, but have spoken to one of his relatives.
Rotorua police have issued a statement confirming the incident.
"As part of the ongoing investigation into the murder . . . police have made numerous background enquiries to establish if there were any incidents or issues relevant to George's murder," the statement said.
"We are aware of a minor road incident that occurred approximately a week prior to the murder. It is one of a number of pieces of information we have identified during the inquiry.
"We are not prepared to comment on whether it has any relevance to the ongoing investigation."
A friend of Taiaroa's, who asked not to be named, said any suggestion he was lazy was ridiculous.
"He was an older guy, and sometimes he would sit down. He had to work in 30-degree heat - he would go through bottles of water."
An Atiamuri resident said locals knew about the earlier incident. If it was the reason for the murder, that was "sick".
"It's not a rational reaction. I would think the person would be deranged."
Taiaroa's family said in March they were at a loss to explain the murder, as George was a kind, gentle man who hated conflict. They could not be reached yesterday.
Police believe the killer planned the murder, and have previously described a strange incident, involving a blue Jeep, shortly before Taiaroa was gunned down.
A farmer who was driving a tractor saw a dark Jeep parked off Ongaroto Rd, and had to steer around it.
The vehicle then began tailing him and made no attempt to pass, even when the road was clear.
The Jeep continued to follow him when he turned on to Tram Rd. As the tractor passed Taiaroa and went over the Tram Rd bridge, the other vehicle dropped back and was then stopped by Taiaroa.
Witnesses saw Taiaroa fall to the ground as a blue 4WD raced away. Police have seized a Jeep they believe was involved, but appear no closer to an arrest.
It is understood the lack of a murder weapon is one factor hampering the investigation.
Police have recovered animals from offal pits on farms they have searched during their inquiry, hoping to find bullets matching the one used in the murder.
- Sunday Star Times