Police say "every line of inquiry" is open in as they investigate Helen Haines's alleged attacker Brendan Nugent. (Supplied)
In short:
Victoria's police commissioner said a reported rift between Brendan Nugent and his family is one line of inquiry as they investigate Monday's attack against Indi MP Helen Haines.
He said Mr Nugent's family had been "very, very helpful" to their ongoing investigation into Monday's attack on Helen Haines.
What's next?
Ms Haines remains in a critical condition, with hospital staff to provide another update on her condition this afternoon.
A reported rift between Brendan Nugent and his family is one line of inquiry for Victoria Police as they investigate the attack on federal MP Helen Haines.
Asked by ABC Mildura this morning if one line of inquiry was that Mr Nugent's alleged attack against Ms Haines was a "proxy" for attacking his family, Victoria Police Commissioner Mike Bush said "yes it is".
"It sounds like a cliche, but every line of inquiry is open ... Every action is under review," he said.
Commissioner Bush said the 43-year-old's father Rod Nugent, and the father's partner Christine Cunningham, had been "very, very helpful" to the police investigation.
The couple released a statement earlier this week in which they said they had been friends with Ms Haines for two decades, and described Monday's events as "devastating and unfathomable".
"We will be assisting Victoria Police in any way we can," they said.
Independent federal MP for Indi Helen Haines remains in a critical condition four days after being rushed to hospital. (Facebook)
Commissioner Bush said the couple were "absolutely cooperating".
"They've been very, very helpful," he said.
"It's an absolute tragic circumstance. As we know, Helen was loved in the community, still is loved and cherished.
"It sounds like a cliche, but every line of inquiry is open ... Every action is under review."
Commissioner Bush said Mr Nugent's interactions with neighbours were also being looked at and that the actions of local police who received those neighbour complaints would be examined.
"They are wonderful people, our police in Wangaratta, they come to work every day and every night to do the best," he said.
Ms Haines, 65, remains in a critical condition at The Alfred hospital in Melbourne, with the staff to provide another update on her condition this afternoon.