The man left the rest of the gear, which Mr Cassidy said was "quite marketable", just metres from the tents he had just broken into.
"This is very unique, particularly in recent months where we've had people taking all types of electronic items, with laptops and digital cameras at the top of the list," said Mr Cassidy.
"It's a bit scary. No one would have heard anything ... It's the first time we've come across something like this," he said.
English tourist Chris Roberts - who is in the middle of a 12-month world trip with his partner, divided into three-month stays in South America, New Zealand, Fiji and Australia - said he was considering abandoning the New Zealand leg of their tour following the incident.
Mr Roberts estimated up to seven vehicles and tents were targeted in the raid.
He said a Korean tourist woke to find the intruder in his tent.
He chased the man, who was last seen jumping over a fence at the camping ground.
"They just leave you feeling absolutely violated," Mr Roberts said.
Just days earlier, Mr Roberts had been at the Top 10 Holiday Resort in Taupo when thieves targeted three four-wheel-drives.
The incident has left Mr Roberts and his partner feeling "really, really unnerved".
Staff at the camping ground would not discuss in detail what happened.
A woman who works at the camp, but did not wish to be named, said the thefts were "a sad indictment on New Zealand".
"It's actually quite frightening, isn't it?"
The Cozy Cottage park owner said thefts involving tourists were common, but not usually at camping sites.
Staff worked very hard to make the place "a safe haven", she said.
A police dog searched the scene following the thefts, and fingerprints were lifted.
Mr Cassidy said the intruder was wearing a white ski mask and was tall and thin.
