Luke Batty was beaten, reportedly with a cricket bat to the head, soon after training with his junior team on Wednesday evening at the Tyabb oval on the Mornington Peninsula, 100 kilometres southeast of Melbourne.
He suffered significant injuries and died at the scene. Reports said he was also stabbed, although this could not be confirmed.
Police said they arrived to find the father Greg, 54, armed with a knife. When capsicum, or pepper spray failed to subdue him, he was shot once in the chest.
The man was airlifted to hospital but died early Thursday.
"I confirm that the male shot by police is the father of the child who is deceased and we're not looking for anyone else," police commander Doug Fryer told reporters.
"I can say the injuries are significant, clearly they caused his death, quite brutal, but I can't go into exactly what they were."
He added: "We're just putting the pieces together still."
The tragedy left mother Rosie Batty, originally from Britain, traumatised. She was just metres (yards) away when the attack took place.
She told reporters her estranged husband had a history of mental illness and was the subject of an apprehended violence order, but it allowed him to visit the boy at his cricket training.
"It was just a little cricket practice. There was people there, I believed he was safe," she said, adding that there were no signs he would ever hurt their son -- their only child.
"Luke came to me and said, 'Could I have a few more minutes with my dad?' because he doesn't see him very often and I said, 'Sure, OK."
She added: "I'm still dealing with disbelief.
"I want to tell everybody that family violence happens to everybody no matter how nice your house is, no matter how intelligent you are, it happens to anyone and everyone and this has been an 11-year battle."
Fryer said there were multiple witnesses to the boy's death, including children and other parents, and they were being interviewed, but refused to release any further details.
Tyabb is a small community of just 3,300 people and the events had left it devastated, Fryer added.
"It's a shocking time for everyone down there. The family, the community," he told reporters.
Flowers were placed at the oval on Thursday by locals, who said they were stunned.
"How could you harm anyone -- but an 11-year-old boy?" Taylor Cuthbertson, 15, told reporters, adding that a friend saw the attack and was having difficulty coping.
"He's really down. He's just completely empty."
Batty attended the Flinders Christian Community College in Tyabb, and in a statement the school said it was bringing in counsellors and chaplains to help parents, students and staff cope.
"Our school community is in shock and struggling to come to terms with these tragic circumstances," it said.
