The province's Special Investigations Unit is investigating the death of a 43-year-old man in Bolton, Ont., on Monday afternoon.
The SIU says at about 1:45 p.m., numerous calls were made to 911 about a man in a vehicle in a business parking lot in the community northwest of Toronto.
OPP officers from the Caledon detachment found the man and arrested him, then called for paramedics due to concerns about his health.
The unidentified man was taken to hospital where he was pronounced dead at about 4:30 p.m.
The SIU has not commented on what may have been ailing the man at the time of his arrest. A post-mortem is scheduled to be held on Wednesday.
The SIU investigates all reports involving police where there is death, serious injury or allegations of sexual assault.