A teenager trying to impress a girl threw a party that spiralled out of control after she posted an invitation to it on Facebook.
Callum Tilbury told the Herald he invited a young woman to a house in Hamilton where he lives with his mother Dawn, who was home at the time of the party, on Saturday night where 10 of his friends were enjoying a few drinks.
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He said the girl posted the small gathering's whereabouts on Facebook and hundreds of people he didn't know began showing up at the small garage in the space of a few hours.
The unemployed 18-year-old said he had "security" at his driveway to stop gatecrashers "but it kinda got on Facebook and the address kinda got online and people started getting crazier and crazier".
"There were so many people that it was crammed, it was just packed on the driveway.
"There would have been about 500 people here, easy."
Dawn Tilbury told the Herald she tried to shut the party down but numbers had swelled so much that she could hardly move outside her home.
She said she was terrified.
"Police came twice and asked to shut it down, the third time they asked me if I wanted to shut it down and I said "f*** yes"."
Hamilton police, who had cordoned off any entry to the street, said that as the partygoers left, they began gathering on the street and then started throwing bottles and other items at police.
Fights then broke out among the large group of mainly youth, with more items thrown at officers. Senior sergeant Pete van de Wetering said officers armed with shields and wearing protective riot gear found "hordes of drunken young people", some of whom were armed.
"Unfortunately some of them ran really out of control and caused damage to a number of neighbouring residential properties, again minor damage, but stuff that would upset homeowners and even frighten them for a while during the night while it was all happening," he said.
"This is a reminder to people who want to host a party to be very careful, in this day of social media, on how we extend those invitations because it's easy for rogue elements of society to get that information and then cause unnecessary trouble, like what happened last night," he said.
Social media commentator David Slack said little could be done to stop the "tidal wave effect" of open invites to parties that go viral.
"I don't think there's any means we have of controlling social media in a way that wouldn't be draconian, to choke off parties like this.
"The most we can hope for is that anybody who does this stuff suffers some kind of consequence that deters other people. For example, a bill from police."