Walsh, 55, was found with multiple stab wounds at his family's Somerton Park home at 2am on Friday.
Adelaide coach Phil Walsh has been found dead. Photo: David Mariuz
He died at the scene, despite the efforts of ambulance paramedics. His wife Meredith suffered a leg injury.
Walsh's 26-year-old son Cy has been charged with murder and is undergoing a psychiatric assessment in hospital, police said. He is expected to face a bedside hearing on Friday afternoon.
Superintendent Des Bray told reporters at the scene on Friday that a knife was used in the attack.
Cy Walsh (left) has been charged with murder.
"At this stage, we won't say what sort of knife, or how the knife came to be there," he said.
Walsh's son allegedly left the scene and was found soon after by police in the suburb of Glenelg East, Superintendent Bray said.
"He's now at the Flinders Medical Centre with police," he said.
Phil Walsh and his wife Meredith. Photo: Facebook.
South Australian police issued a statement about 12.30pm on Friday asking members of the public who may have seen Cy Walsh on Brighton Road in the early hours of the morning to come forward.
"Police believe he was walking north along Brighton Road towards First Avenue, Glenelg East, between 1.45am and 2.30am this morning," the statement reads.
The 26-year-old was wearing a dark top and dark pants, with grey and brown Converse shoes, police said. He is described as being about 185 centimetres tall with a thin build and blond spiky hair.
Phil Walsh, his wife Meredith and their children. Photo: Facebook.
Superintendent Bray said Walsh's son lived at the Bungey Avenue house with his parents.
Ambulance paramedics contacted police after receiving an emergency call about a stabbing, he said.
"Somebody from the house called triple-0 and asked for an ambulance and the ambulance contacted police," Superintendent Bray said.
Police outside the Walsh's Adelaide home. Photo: David Mariuz
"Shortly after, police and ambulance arrived at about the same time. Two patrols attended with ambulance crews.
"Ambulance crews immediately rendered first aid and tried to resuscitate Mr Walsh, but unfortunately a ... doctor declared that he had died shortly afterwards."
Walsh's wife was treated by paramedics at the scene, before being taken to the Flinders Medical Centre with non life-threatening injuries.
Police outside the home of Phil Walsh. Photo: David Mariuz
It is understood Walsh's daughter is overseas on holidays.
Superintendent Bray said the incident was tragic, regardless of Walsh's high profile.
"It's not even just that he's a high profile person, it's just absolutely terrible when families are torn apart in such tragic circumstances," he said.
"For any family, regardless of who it is, [this is] one of the worst things you could imagine that could happen to you. The pain and suffering of the family is no different."
Shocked Adelaide Crows players were seen arriving at Adelaide Oval on Friday morning.
The Adelaide Football Club released a short statement soon after, saying they were devastated by Walsh's death.
"The Adelaide Football Club is devastated at the sudden passing of senior coach Phil Walsh in the early hours of this morning," the club said.
"We ask if you could please respect the privacy of his family, as well as our players, coaches and staff, at this extremely difficult time."
The club said it would hold a media conference on Friday afternoon.
The AFL is yet to comment.
The Crows are scheduled to host Geelong at Adelaide Oval on Sunday. That match is now in doubt.
There has been an outpouring of grief and shock on social media, as the community and football world reach out to the club and Walsh's family.
AFL great Wayne Carey tweeted: "Thoughts are with everyone that Phil Walsh has touched on this very sad day #shattered."