An 18th birthday party that went viral on Facebook caused "chaos" with rocks and bottles thrown at police in riot gear, neighbours robbed, two vehicles stolen and road signs smashed the length of a rural Tai Tapu road.
Two utes were stolen after riot police split up the Friday night party in Early Valley Rd.
One of the utes was found torched about a kilometre down the road, while the second ute was found at the Izone industrial park, in Rolleston, this morning.
Constable Herb Inwood said a firearm left inside that ute was missing.
He was concerned the high-calibre rifle, which was hidden under clothing in the back seat, may end up "in the wrong hands".
"It's a concern. We don't know where it is," he said.
Inwood hoped the teens had tossed the rifle and it was lying in a ditch somewhere.
A $120,000 Hummer, stolen the next night during another party at the same property, was found in New Brighton about 11.30pm yesterday.
"It wasn't burnt out, it was there parked up."
The Hummer, which belongs to Peter McKenzie, was being held by police to undergo a forensic examination, he said.
Both parties were held at McKenzie's Tai Tapu property.
Inwood said the McKenzies, who had lived in the area for about 20 years, had been holding parties at their property "since the boys were old enough", without incident until Friday night.
He said McKenzie's boys expected only a "couple of hundred" people to attend, but the party got "out of hand" after being shared on Facebook.
Even police officers with children had seen the post shared on Facebook prior to the party, Inwood said.
The incident showed parents or organisers needed to ensure they had adequate security in case things got out of control, he said.
It also came as a warning to teens to consider what they posted on Facebook as it may have a much wider reach than they expected, Inwood said.
The event on Saturday night was organised by Cashmere High School's pupils as an after-party for their ball.
The party was not sanctioned or associated with the school, Cashmere High School principal Mark Wilson said.
He was not aware the event had been organised.
Wilson said a letter was sent out to parents prior the ball outlining the school's expectations of the students, and the teens were made aware during an assembly.
"What students get up to in their own personal time is the responsibility of themselves and their parents," he said.
Police were investigating both incidents, and McKenzie was reeling at the power of the internet and the fact about 1000 teens turned up before a "major crime spree" ensued.
"It's a bloody nightmare," McKenzie said.
"I probably deserved it because I half-pie invited these people on to my property."
He only wanted to "give these kids somewhere to go".
"They have their ball or whatever and I, out of the goodness of my heart, said you can have it here."
He felt sorry for his neighbours, would not be hosting any more parties "in a million years", and would clean up the mess along the rural road.
Neighbour Andrew Nicholson said while the second party was less out of hand, it was on top of what he described as "a Mad Max scenario" on Friday night.
"It was complete anarchy. Teenagers p....., out of control, and with no respect for anyone else.
"The neighbourhood is fizzing."
Another neighbour said he saw 13 police cars, two police vans and police in riot gear turn up to the Friday night party.
There were about 20 mailboxes and road signs smashed in both Early Valley Rd and Old Tai Tapu Rd.
A pensioner whose ute was stolen and burnt out was so traumatised he called a neighbour upset at 3am when the Saturday night party kicked off.
"You can only describe it as riotous behaviour. We've all had a gutsful," said one resident who said he had a pitchfork at the ready inside his front door on Saturday night.
Jonny Martin, 18, and his two friends rent a house on McKenzie's property and were not involved in organising the party.
The paddock it was held in was part of their lease, and they said they had not given permission for the 1000-invite event to take place.
On Friday the young men saw rocks and bottles being thrown at police, which prompted officers to respond in riot gear.
Partygoers had run through their house trying to seek refuge from police, and the flatmates found one partygoer using their stovetop to take marijuana in their kitchen.
"It was chaos," Martin said.
Martin said two iPhones and an iPad were taken from their rooms.
Inwood said no police were called for the Saturday night party but he would investigate the stolen Hummer.
The Saturday-night party organiser, who would not be named, said that event went "pretty smoothly".
There were about 300 tickets sold to the party held in a hireable inflatable cube at the Tai Tapu property.
"It had lots of security and it was fun."
Anyone with information in regards to the stolen Hummer is asked to call the police on (03) 363 7400. Any information in relation to Friday night's party is asked to call (03) 325 2800. To provide information anonymously call Crime Stoppers on 0800 555 111.
- © Fairfax NZ News