A Special Investigations Unit logo can be seen in this undated file photo.

A Petrolia man at the centre of a Special Investigations Unit investigation (SIU) has died from his injuries sustained from a self-inflicted gunshot.

On Monday, Oct. 26, Lambton County OPP responded to an address in Petrolia for a man in mental distress.

Police initially responded around 7:30 p.m., nearly three hours later the Emergency Response Unit located the man at the back of the residence suffering from a self-inflicted gunshot.

He was taken to hospital where he remained in critical condition until Sunday when he died as a result of his injuries.

The SIU was called in to investigate as they are mandated to investigate any police interaction where there has been a death, serious injuries, or sexual assault.

The SIU says they are continuing to investigate the circumstances of this case.