Paul Costa was wearing an expensive suit when his body was found bloodied and face down in a Melbourne park almost 12 hours after he went missing.
The 43-year-old Coburg man was found dead in Dunstan Reserve in Brunswick West on Monday morning.
"The homicide squad is investigating Paul's death and it is being treated as suspicious," police said in a statement on Wednesday.
Mr Costa was found wearing an Ermenegildo Zegna suit and expensive dress shoes, and there was a blood trail leading from the car park to the body.
His father Alex said he thought his son may have been going on a date.
"We don't know why he was wearing his suit and dress shoes," he told the Herald Sun.
"He was very private, we thought he had a date.
"He was very kind, he wouldn't even hurt a bird."
Mr Costa was last seen driving away from his home at 9pm on Sunday, before his body was found at 8.20am on Monday.
Police have released a photo of his missing red 1999 Nissan Patrol, with the registration PJJ199.
They want to speak to anyone who spoke to Mr Costa on Sunday night or who knew why he was at Dunstan Reserve.