The star had just celebrated his first wedding anniversary with wife Lizz.
The pair married in April last year, 18 months after meeting on Instagram.
Pua also leaves behind a young daughter from his first marriage.
The shock news has been met with an outpouring of heartfelt tributes.
Speaking from Samoa, actor and writer Oscar Kightley - who worked with Pua on Sione's Wedding - led condolences saying he was as "shocked as everyone else".
"I'm just really feeling for his family."
Dame Valerie Adams tweeted her shock, saying her "thoughts and prayers" were with Magasiva's family.
If you or someone you know needs help, contact Lifeline on 13 11 14 or visit their website at www.lifeline.org.au