The camper pleaded with him to hand over the weapon.
"You sat there with the firearm in your right hand, resting the barrel on your forearm and pointing it directly at this complainant," Judge Charles Blackie told Keefe-Wilson when he appeared in Whanganui District Court this week.
"You pointed the gun at her saying, 'I'll f*****g shoot you' and she replied, 'do it then'."
Judge Blackie praised the courage of the victim, who eventually convinced Keefe-Wilson to hand the magazine to her, before throwing it away when he demanded it back.
By this stage, police had been called and they arrived as Keefe-Wilson was chasing a number of campers with his car.
"At this point there were about five members of the public in the rear of a campervan, seeking refuge from what was an escalating situation," Judge Blackie said.
"Another person was standing outside the campervan; he got out and you approached him. You then put the firearm to his back and he had to enter the campervan."
Keefe-Wilson made one of his victims drive the campervan, stopping when they came upon police officers.
The campers managed to jump out of the vehicle and flee, while Keefe-Wilson pointed his rifle at the officers.
"One of the officers, armed with the appropriate police-issued weapon, fired one shot, which struck you in the arm, causing you to drop the rifle to the ground," Judge Blackie said.
"It was necessary for a dog to be released into the campervan to secure your exit and even then there were violent struggles."
Police administered first aid to Keefe-Wilson and then arrested him.
On Wednesday, Keefe-Wilson was sentenced to six years and three months imprisonment.
He pleaded guilty to 12 charges — six of kidnapping, two of using a firearm against law enforcement, two of assault with a weapon, unlawfully carrying a firearm and threatening to kill.
Keefe-Wilson, his partner and her seven-year-old son drove to Vinegar Hill on December 15.
The day before his arrest an altercation broke out between him and his partner.
"You began to verbally degrade your partner, calling her a useless bitch and telling her to do some cooking for you," Judge Blackie said.
"At one point, you held the barrel of the firearm against her head.
"You said to her, 'I should just shoot you now — you think I'd have a gun at your head if it didn't work? Shall we give it a go? If I f*****g catch you, I'll f*****g shoot you in the head'.
"This must have caused her to be absolutely petrified."
Before sentencing, Crown prosecutor Deborah Davies submitted that Keefe-Wilson deserved no discount for mental health.
"It's not as a result of a mental health condition — it's because he had taken methamphetamine — in his own words, about 10 times — since he'd been at that camp.
"This defendant has 26 previous convictions, so he's got quite a history. He has committed this offending because he's under the influence of methamphetamine."
Defence counsel for Keefe-Wilson Jacinda Younger opposed the Crown view on mental health.
"I am suggesting to the court, and have gone to great depth to do so, that this defendant's drug addiction and mental health are interrelated," Younger said.
"He began his methamphetamine addiction when he was 12."
Younger submitted that methamphetamine alters the structures of the brain and said that Keefe-Wilson instructed he was using because of the paranoia he was suffering.
Keefe-Wilson believed Whanganui gang members were after him, his partner and her son, which was the reason he grabbed a gun and fled to Vinegar Hill.
Younger said that Keefe-Wilson had tried to get help in June 2017, about six months before his offending.
"He reported to Whanganui Mental Health, explained to them that he was working and was free of methamphetamine, but was struggling with his mental health.
"It is a travesty that he was turned away and not medicated."
Judge Blackie took Keefe-Wilson's mental state into account in his sentence and ordered that he go before a parole board at the earliest possible time.