The South Australian policing family is in mourning after an officer was killed in a shootout - the state's first police death in the line of duty in more than 20 years.
Brevet Sergeant Jason Doig and colleagues Michael Hutchinson and Rebekah Cass were on a "routine" assignment to a rural property in Senior near the Victorian border about 11.20pm on Thursday to investigate an incident involving the use of a firearm and an animal.
They were confronted by an armed man who fatally shot Sgt Doig, 53, a police veteran of 34 years.
Sgt Hutchinson, 59, was also shot and taken to Adelaide for treatment. Constable Cass, 31, was uninjured.
The male suspect, 26, was shot by police and sustained serious life-threatening injuries. He remains under police guard at Flinders Medical Centre.
"This is a devastating day for South Australian Police," Commissioner Grant Stevens told reporters on Friday.
"No one is left untouched by this tragic incident."
Mr Stevens said there was no indication the officers were going into a high-risk situation.
The full circumstances of the incident will be the focus of a commissioner's inquiry, with investigators still at the scene on Friday.
Flags will fly at half mast across the state while funeral arrangements are worked out.
The policing family is "in shock, in pain and in grief" after losing a brother, the Police Association of South Australia said.
"Today, the collective heart of the nation's police is broken and, right now, it feels broken beyond repair," president Mark Carroll said.
"This horror is what all of us in policing live in fear of - it is our dread, that one of us or one of our workmates has his or her life taken.
"I make crystal clear our intention, as police and as a union, not to allow Jason or his family to be cheated of a scintilla of the justice they're determined to be owed."
Premier Peter Malinauskas said the tragedy was especially acute after Sergeant Ian Todd and Sergeant Jordan Allely were brutally stabbed in the mid-north town of Crystal Brook in May.
He said he was concerned about a "pattern" of violent behaviour against police, including the fatal shooting of two police officers in Queensland last year.
"One can't begin to imagine what was going on in the life of the alleged shooter to provoke him to conduct this act," he told reporters.
"But the fact we're seeing more than one incident now around the country does beg the question what is going on."
Mr Stevens said officer safety was paramount and police are provided with the right tools, equipment and training to do their job as safely as possible.
"But you cannot get past the reality that police are often involved in dealing with violent offenders," he said.
Sgt Doig was officer in charge of Lucindale Police Station - a "highly respected" career officer who had served the local community for 15 years.
The last SA police officer killed on duty was Snr Const Bogdan Sobczak, a motorcycle officer who died in a road crash in 2002.
The alleged shooter's family said their thoughts were with the family of Sgt Doig and Sgt Hutchinson.
"Our hearts are broken by the incidents that occurred overnight," the Stimson family said in a statement.
Federal Attorney-General Mark Dreyfus said all Australians stand with police officers across the country grieving the loss of one of their own.
Opposition Leader Peter Dutton - a former Queensland police officer - said Sgt Doig was "a remarkable Australian who embodied the very best of Australia".
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