Family and friends of an Australian man killed in an altercation outside a San Francisco hotel say they are stunned at the loss of the fun-loving sportsman who was "not a fighter".

Matthew Bate, 33, was rushed to hospital but died after the incident, which happened in the early hours of Friday outside the Da Vinci Villa Hotel.

His cousin, Colin Bate, said on Sunday he was still reeling from the news.

He had only heard that Matthew, better known as Matt, "got punched and his head hit the ground. I don't know much more than that". 

Matt, who was single, had been living in Darwin for a year, working as an analytical chemist.

Most of his family lives in Ocean Grove, south-west of Melbourne, where he had lived since childhood.

It's believed he had been travelling in the US with three Ocean Grove friends. 

San Francisco homicide police initially detained two men. They later said one had been arrested.

Matt's devastated parents and sister have flown to the US to retrieve his body, and a memorial service is being planned for Tuesday in the beachside town, possibly at the football club.

The Bate family said in a statement: "He had such a warm and kind soul and was a wonderful son, brother, uncle and friend".

Colin told Fairfax Media: "it's pretty hard to take in, actually, at the moment". 

He said his cousin was "pretty solid", about six feet tall, but wasn't a fighter.

"He was pretty friendly, fun loving and liked to enjoy himself. He wasn't a fighter. I can't believe it to be honest.

He wasn't aggressive, put it that way."

Peter Hart, president of the Ocean Grove Cricket Club, where Matt had played as a leg spinner, said he was "a very fun-loving individual".

"He enjoyed life, enjoyed having fun. He was never a problem to anybody, never a harm to anybody, wasn't an aggressive sort of a person at all. He'd rather put his arm around you and have a joke with you," he said.

"It's a bit of a shock to the community. Everyone knows the Bate family in Ocean Grove."

Colin Bate said his own father, Richard, and Matt's father, Graeme and their families had moved from the Sunshine area to Ocean Grove about 22 years ago. 

They became immersed in local football and cricket, both playing and administration. Matt had played both sports and was a keen golfer.

Matt attended Bellarine Secondary College before getting a degree in geology. He worked for Barwon Water, before moving to Darwin for work. 

Colin, who runs an Ocean Grove concrete-cutting business with Matthew's brother, David, said the family and the close-knit community had been struggling to come to terms with the tragedy.

"I think it was a bit of a shock to the whole town, to be quite honest, with a lot of people getting in touch with our whole family, getting behind us."

With AAP