A Club Habitat staff member said they had been instructed not to speak to the media but the incident was shocking, "especially seeing it's just a few days before Christmas''.
Holiday Parks Association chief executive Fergus Brown said staff were shaken.
"They're very distressed about the whole situation,'' he said.
"We're very sad that this has happened and our thoughts are with the family, but it's very much an isolated incident. But it's very, very sad, especially at this time of year.''
Mr Brown said he did not think the incident would deter tourists from staying at holiday parks in New Zealand.
"Unfortunately crime happens throughout the world and New Zealand has its fair share, but we're definitely a reasonably safe country to travel in.
"Holiday parks have always been known as safe places to stay at, so we're very, very concerned about this happening.''
Mr Brown said parents should always take care with younger children at holiday parks, many of which were next to beaches, rivers or lakes.
"But I think we are definitely not in the situation where we are in any heightened state of alert for safety at holiday parks.
"Holiday parks have always been known as very safe places for families to stay at, and it is the iconic New Zealand holiday, going to stay at the camping ground.''
Detective Inspector Mark Loper, who is leading the investigation, said the timing made the attack worse.
"This is a vicious attack, and the fact that it is on a 5-year-old tourist just days before Christmas makes it all the more appalling. It is vital that anyone who has the smallest piece of information that might help this investigation comes forward as soon as possible,'' Mr Loper said.
ESR were carrying out a scene examination and police were interviewing the parents.
Bay of Plenty District Commander Superintendent Glenn Dunbier said the family were overwhelmed by the support they had received from emergency services.
A media conference will be held this afternoon in Turangi.
