A teenager who allegedly stabbed his mother to death in White Gum Valley on Monday night may have had a psychotic episode after earlier seeking hospital treatment.
The major crime squad is investigating the death of Joan Hendry, 52, who died after an apparent frenzied incident at her Stevens Street house just after 11.30pm.
Ms Hendry's 19-year-old son Gabe Lang is in hospital with critical injuries from what are believed to be self-inflicted knife wounds.
"We saw him come out and fall into a car bonnet with what looked like a stab wound on his neck," one neighbour said.
Several neighbours said they heard screams coming from the house before the sound of sirens.
Ms Hendry's partner Bruce Abbott and her daughter Rosie Lang were also injured in the incident that left a community bewildered and heartbroken.
"It is such a tragedy and will be a big loss," Frank Sander, Ms Hendry's friend of more than 20 years, said.
"People are looking for answers.
"We called her Joanie the one and only - she was a very exquisite woman."
Mr Sander's partner Chadia Scheel was visibly shaken yesterday as she came to terms with the loss of her friend.
"She was my closest friend," she said.
"We know everything about each other - there was nothing we didn't talk about."
It is understood Ms Hendry took her son to Fremantle Hospital Mental Health Service on Monday evening.
It is believed the pair did not make it in time for the centre's 8pm cut-off, so were sent to Fremantle Hospital's emergency department.
Ms Scheel said that Ms Hendry and her son went home after waiting about 2 1/2 hours in emergency.
It is unclear whether Mr Lang had medical treatment when his mother brought him in.
Mr Sander and Ms Scheel described Mr Lang as a gentle person and said this act was extremely out of character.
Close friends gathered near the family's house yesterday afternoon, which forensic investigators cordoned off along with neighbouring houses.
Ms Hendry was a registered nurse, an artist and much-loved community member.
Family friends told _The West Australian _she was a loving mother who tried to help her son overcome mental health problems.
Detectives are waiting to speak with Mr Lang, who yesterday was in a critical but stable condition under police guard in Fremantle Hospital.
A hospital spokeswoman would not comment on claims the family sought help for Mr Lang on Monday evening. "All people have a right to confidentiality of their personal health information," she said.
"Therefore the Department of Health will not comment on matters or answer questions where personal information is being sought."