Bill Gardian wants to know why and how his son Chris died.

The 39-year-old Toronto man died six days after being taken into police custody in January.

Gardian has a stack of pictures and documents related to his son's final days. "I just felt I owed it to him to do this investigation," he said.

Chris Gardian and Veronique Mavre shown in a photo taken the day before his death. (CBC)

Chris was an alcoholic, living on the streets in Toronto when he had a run in with police.

Chris Gardian and Veronique Mavre were drinking with friends near Spadina Avenue and Nassau Street in Kensington Market, when police showed up.

"They just went in and running at him and pushed him. And he went flying face down on the pavement over there," Mavre told CBC News.

Mavre says officers also kicked him.

"They jumped on him and when he was handcuffed face down. They were still kicking on him," she said.

Bill Gardian says the EMS records back up that version of events.

"[The EMS records] indicated that Chris had been elbowed from the back of the head — and I guess he went face forward down to the pavement and hit his face and lost consciousness."

One document shows police initially arrived on scene thinking it was a sexual assault but that charge was never laid.

Gardian went to hospital, then jail. He was charged with assault.

Four days later he was released.

Two days after that he died in his sleep.

Bill Gardian has taken all the information he has collected to Ontario's Independent Police Review Board and the OIPR is investigating.

He says he's not challenging the cause of death.

"The autopsy concluded it was booze — and an alcohol withdrawal drug — something Chris was given in jail.

But he wants to find out if the justice system dealt with his son properly.

Bill Gardian wonders if police went too far — and wants to make sure they treat homeless people fairly.

"I get worried that they're just discarded and they can be someone's son or daughter," he said. "I just felt I owed it to him to do the investigation," he said.

Toronto Police won't comment on the case, saying it's under investigation.