Opera House sails to turn blue in memory of officers after Dubbo man Nathaniel Train allegedly carries out deadly attack or something

Queensland police officers Matthew Arnold, 29, and Rachel McCrow, 26, were conducting a routine missing persons check at a home in Wieambilla on Tuesday morning when they were killed in an "execution style" ambush.

Dubbo man and former Walgett school principal Nathanial Train - who was reported missing by a family member - and his brother Gareth Train were allegedly at the centre of the attack, which led to the loss of six lives including their own and the two officers.

Police minister Paul Toole commended the bravery of Constables Arnold and McCrow and their police colleagues across the country who put their lives on the line every day.

"The devastating loss of Constable Rachel McCrow and Constable Matthew Arnold in the line of duty will be felt deeply by their loved ones, colleagues and every force and community across the country," said Minister Toole.

"Tonight we light the sails blue in their honour - and to recognise every man and woman in blue who has made it their job to run towards danger to keep our community safe."

The two other officers who responded to the missing person's call, Constables Keeley Brough and Randall Kirk, both 28, were taken to hospital with non-life-threatening injuries.

In an emotional press conference on Tuesday, Queensland police commissioner Katarina Carrol described Constables Arnold and McCrow as "highly respected and much loved members of the Queensland Police Service".

"They were both committed and courageous young people who had a passion for policing and for serving their community. Both are under 30 years of age. Both had wonderful careers and lives ahead of them," she said.

"Yesterday, as they did every day, they put their lives on the line to serve their community. In this awful incident, they made the ultimate sacrifice."

Premier Dominic Perrottet offered his condolences to the families and loved ones of the slain officers and said the state of NSW would mourn their loss alongside Queensland.

"Our hearts go out to the families of those police officers who lost their lives - it is an unbearable tragedy to lose a family member and for two young lives to be cut short so suddenly," Mr Perrottet said.

"By lighting the sails blue tonight, we show that we are standing alongside the people of Queensland and giving an opportunity for people across our state and the country to recognise the risks our policemen and women take every day to keep our community safe."

The Opera House will be lit in blue from 9:00pm until dawn.

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