A groom is in mourning after two members of his wedding party were killed in a crash that took the lives of three Kiwis in Western Australia over the weekend.

Police confirmed those killed were aged 24 or 25, but have not released their names.

The West Australian named them today as former Southlanders Dylan Sherriff, Jeremy Vergeer and Kadin Wallace.

Childhood friends killed in crash in Western Australia


They also reported Mr Vergeer became engaged to his girlfriend this month, and his fiancee, Lauren Withers, posted a heartbreaking tribute on Facebook to the young father this afternoon.

"You were my soul mate, my best friend, my everything. The future seemed so promising for us and I struggle with the idea that it's now all just a beautiful dream I had. We talked about the future with so much happiness and excitement and I will hold onto that feeling forever. '2016' was going to be the best year for us, buying our first home, getting married and moving to NZ to start our family. We really where both so unbelievably happy ... I know your (sic) here with me now, you will watch over me and your beautiful little boy ... who you loved so deeply."

Former Southlander Rory Watt, a close friend of the trio, called his father Tony on Saturday with the devastating news.

"He was a mess. He's due to be married in Perth in July and it's his best man and ... groomsman. Two of them were to be in his wedding party," Tony Watt said.

Paramedics were called to an unsealed stretch of the Lake King-Norseman Rd, at the eastern edge of the wheatbelt region, about 400km southeast of Perth, about 7.30am on Saturday. The West Australian reported the men were understood to already be dead when a passerby found the wreckage of their Toyota Hilux dual-cab ute, which had been badly damaged after rolling.

Crash squad detectives are investigating and a Western Australia police media unit spokeswoman told the Herald today there were no updates on a possible cause.

Mr Watt said the dead men grew up in central Southland but, like his son, had lived in Australia for several years, Mr Watt said.

"They worked for crop farmers. They were just good Kiwi boys, they loved their hunting and fishing. We don't know what happened. Rory last heard from them when he got a Snapchat from Dylan at 10pm."

According to his Facebook page, Mr Wallace was from the tiny Southland settlement of Nightcaps.

A man who identified himself as Mr Wallace's brother did not want to comment when contacted by the Herald. No one from Mr Vergeer and Mr Sherriff's families could be contacted but a friend from Esperance told The West Australian the three men were "some of the most genuine guys you could ever meet".

"They all came from New Zealand and were best of friends. It's just a tragedy. They just worked every day and worked hard and they all hung out together."

Another friend, Kane Puki, wrote on Facebook that it was an honour to spend three months in Esperance "with ya's doing what ya's did best, get s***faced and do outrageous fun activities. RIP men."