His death was confirmed by Widnes.
Australian media reported that Ottio collapsed after a long training run with players from the PNG Hunters in Port Moresby and died later in hospital.
Marum said numerous players, who gathered outside Ottio's family home wearing their 2017 grand final T-shirts, would need support, including Albert, who was due to share a house in Widnes with Ottio.
Ottio signed for Widnes at the end of past year from Australian National Rugby League team the Canberra Raiders.
Papua New Guinea global Ottio, who represented his country at last year's World Cup, was due to travel to join Widnes for pre-season training after signing for them in December.
"This news is all the more tragic, because Kato was due to travel to the United Kingdom this week to fulfil his dream of playing first-grade Rugby League".
Ottio never played an NRL game, but led the try scoring during the 2016 NSW Cup for Mounties and scored a try in last year's World Cup.
Raiders coach Ricky Stuart said he was knocked for six when he heard the devastating news.
"He could have become a real hero with our supporters with the way he played", chief executive James Rule said.
'It's hard to believe because we had just got bedding and other things like crockery today for the place where he and Wellington were going to live.
"He was a very respectful young man who appreciated everything we were doing for him here in adjusting to life in Canberra and learning his trade in becoming a professional football player".
Widnes coach Denis Betts also spoke on the tragic news, extending his condolences to Kato's family and paying tribute to the player's "incredible gifts". "Moreover, in all our interactions with him, we found Kato to be a person of great character who was excited to be following his dreams".