The Bourke Street killer fancied himself as a police informer in the days before he ran down and killed six people in Melbourne in a stolen car.
An inquest looking into the police response in the days prior to the incident has heard James Gargasoulas was paranoid and deluded before the rampage on January 20, 2017.
"The offender was trying to impress me the whole time," said Detective Senior Constable Murray Gentner, who interviewed him six days before the killings.
"He thought he could come and work for me. He wanted to be an informer. He was basically saying he could help me solve a murder. He was deluded."
Gargasoulas was being interviewed following his arrest earlier that day for threatening to kill a family member with a knife and was waiting for a bail justice.
The detective said he first encountered the offender in December 2016 and knew him to be involved in drugs and stealing cars.
He said he realised Gargasoulas was deluded when he asked during his interview why police wanted to kill him.
Despite police opposition that he posed an unacceptable risk to public safety, he was bailed and in ensuing days his behaviour escalated, the detective said.
Det Sen Const Gentner is continuing his evidence today.