It was pitched as a case of a good Samaritan being turned on, but police say it turns out all were involved in criminal activity.
In late March, police called for help from the public to catch an assailant who turned on a motorist that had stopped to provide assistance.
"At around 10:30pm a man stopped at the Eastburn Road layby on the Queenstown side of the Crown Range after noticing an unknown man signalling for help using a cellphone torch," police said in a statement on 27 March.
"After stopping and getting out of his car, the victim was asked to look at an issue with the other man's vehicle.
"As the victim turned away he was punched several times by the man, who then grabbed the victim's backpack and drove off in an unknown direction.
"The victim was able to drive to a family member's house, where police have been called and he has been taken to hospital. He is currently awaiting surgery on a fractured jaw.
"This was a cowardly attack on a well-meaning person who was trying to help someone he thought was in need."
Detective Senior Sergeant Malcolm Inglis said the only problem was that was not true.
"Yesterday a 20-year-old Cromwell man was arrested and charged with the robbery," Inglis said.
He would appear in the Queenstown District Court next week.
But the 21-year-old victim knew the offender and his story did not add up.
"Police enquiries have now established the pair were known to one another and the meeting, which actually occurred in the car park at Coronet Peak, was pre-arranged," Inglis said.
"Police are satisfied that this was not a random attack and that other criminal activity was involved.
"As such, we expect to charge the 21-year-old with making a false statement to police."
He did not detail the nature of the criminal activity that was involved and as the matter was now before court, police would not comment further.