Dr Reddy's remains were found in a suitcase inside her vehicle in laneway at Kingsgate in Sydney's eastern suburbs just before 9.30pm last night. Preethi's body had multiple stab injuries.
Reddy was last seen waiting in line at McDonald's in George Street on Sunday, the police said.
Det Supt Dengate said police spoke with the man before he died in a "deliberate" head-on collision on the New England Highway at Willow Tree, in the Upper Hunter, about 10pm on Monday.
She was attending a dental conference in St Leonards over the weekend and last made contact with her family about 11 am on Sunday, saying she planned to head home after having a late breakfast in Sydney- NSW police said on their website. Police officials said the man died in a auto crash on the New England Highway on Monday night, a day after Reddy was reported missing.
The ABC understands the man who died was the key suspect in Dr Reddy's murder.
Police had issued a public appeal after the disappearance of the 32-year-old woman.
Detective Superintendent Gavin Dengate revealed officers grilled Narde while Dr Reddy was still the subject of a missing person's inquiry after the pair spent Sunday night together.
Police officers searched the vehicle after it was found at Strachan Lane. She then left the restaurant and walked south through the city towards Market Street.
Preethi Reddy was last seen waiting in line at McDonald's in George Street on Sunday
The Sydney Morning Herald reported Preethi's friends as saying that she was firm on her decision to break-up with Harsh several years ago, but the latter did not accept it.
The ex-boyfriend of Sydney dentist Preethi Reddy didn't have a violent history that suggested he was capable of committing the obsessive attack which killed the "bright" young woman.
CCTV footage showed Preethi at a McDonald's inside the Strand Arcade in Sydney's CBD about 2:15 am Sunday.
NSW Police said the investigation was still in its early stages.
In a statement released on behalf of Dr Reddy's family, her sister Nithya said: "Words can not capture the pain we are feeling with the passing of my attractive big sister".
"I ask you all to think about her family right now and about giving them the space to actually to be in this space". Dr. Preethi Reddy went missing on Sunday and the police found her body in a auto trunk.
What is known is her now dead ex-boyfriend, Tamworth dentist Harshwardhan Narde, drove 400 kilometres to attend a dental conference at St Leonards in Sydney's north where he met up with Dr Reddy over the weekend.