"His smile was infectious. He had no shame, was an entertainer at heart and would sing and dance - it didn't matter where he was or who he was with, he just liked to put a smile on everyone's faces.
"It has absolutely shattered our world."
William's mother Marise, father Grant and sisters Sarah, Rebecca and Jessica have gathered with other family and close friends, including his girlfriend Molly, at the family home in Paeroa since learning the tragic news.
"I was in Taupo, Dad was at work and Mum was at home," Sarah said.
"One of the other sisters was just out of Matamata and another was in Tauranga. By 2pm we were all together at home in Paeroa.
"We can't believe it is real. We are missing a piece of our puzzle, not having William at home with us. We liked to be together as much as we could be. We are a mess."
A Givealittle page has been set up to help the family with funeral costs.
William was an uncle to Sarah's 10-year-old son Alex, and godfather to the daughter of one of his best mates.
"He was the best uncle one could ever ask for."
He had been with his girlfriend Molly for 10 months.
"She is heartbroken, and has been with us since Saturday. We are a tight family."
William was the youngest in the family. "The baby," Sarah said.
He was born in Auckland, but the family grew up around the Thames, Coromandel and Hauraki areas.
"Three sisters and a little brother ... the poor boy. We dressed him up, made him wear costumes and makeup, but he had our back.
"He was like a big bro. We are all fairly short, so we'd call him our little bro, but he'd be like, 'No, I'm bigger than you'.
"I went through a break-up not long ago and within half an hour of finding out, William was on my doorstep."
Growing up for the Careys was all about the beach.
"Anything to do with the beach. He spent 17 years of his life, every Easter and Christmas holidays, going up to Fletcher Bay, at the top of the Coromandel, camping.
"We pretty much grew up with fishing rods in our hands. We'd also spend a lot time on the rivers, going down on our boogie boards, camping antics."