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The police have ruled out Ms Haddad's death was accidental or the result of suicide, confirming she was murdered.
Detectives have not revealed why they came to this conclusion.
Previously, Ms Haddad worked as an executive at a WA mining company before her move to New South Wales in 2016.
She moved to Australia in 2007 to work for BHP after graduating with a degree in industrial engineering in Rio de Janeiro.
Police said they were specifically seeking CCTV or dash-cam footage of Cecilia or her car in the Hunters Hill region, Ryde, Top Ryde, West Ryde and Woolwich areas at the weekend.
NSW Police urged anyone that might be able to assist with the investigation to phone Crime Stoppers on 1800 333 000 or Ryde Police Area Command on 02 9858 9299.
Police believe he tried to fire at least twice more, but the gun jammed or he ran out of bullets.
Police said Cecilia Haddad's red-coloured Fiat 500 was found at Ryde train station on Sunday afternoon, more than 24 hours after she called friends and was never heard from again.
'Her ex-husband has spoken with us and is assisting us with our enquiries.
He's very, very traumatised but has been of great help to us.' Police confirmed they had seen Ms Haddad on CCTV footage taken in the Ryde area, but appealed for any security or dashcam footage that may help their investigation.
She was ready to go home after a long day in which her hard-working parents drove her across London to wish her uncle a happy birthday.
Security cameras installed because of the constant threat of armed robbery captured the moment that would change her life for ever.