A police officer in Australia died in front of his future bride when he fell and cut his neck at their engagement party.

Senior Constable Liam Trimmer and his fiancee were with friends and family when the celebration turned into a tragedy.

He slipped at one point and fell. It was unclear what caused the cut to his neck in front of shocked guests.

"Everything was done to try and save him but it wasn't to be and I know everyone that was involved are really, really hurting. I think they wish they could just wake up from this nightmare," WA Police Commissioner Col Blanch told 9NEWS.

Trimmer moved to Australia about 10 years ago from the UK a decade ago and graduated from a police academy in 2013.

He moved to Kalgoorlie in the outback in 2017 and was a member of the police force's gang crime squad and tactical response group, Sky News reported.

The Western Australia Police Union said in a statement that it "sends heartfelt condolences to the family, friends, and colleagues of the fallen officer during this difficult period."

Police are still investigating the case for a report for the coroner. His fiancée was not publiclly identified.