03/29/2015 11:20 EDT | Updated 05/29/2015 05:59 EDT

SIU investigating after man, 58, dead after standoff at Walmart in Peterborough

PETERBOROUGH, Ont. - Ontario's police watchdog is investigating the death of a 58-year-old man after a standoff in a Peterborough parking lot that forced a lockdown at a Walmart on Saturday.

The Special Investigations Unit says Peterborough city police were contacted about a man with a firearm.

An SIU statement says officers located the man in his vehicle in the store's parking lot and tried to communicate with him.

The agency says a gunshot was heard from the man's vehicle and police found the man dead.

A post-mortem has been scheduled for Monday morning in Toronto.

Local media outlets reported there were several hundred of people in the store at the time.

Peterborough paramedics were called to provide assistance to any customers at the supermarket who required medical attention, but no injuries among the customers were reported.