The province's Special Investigations Unit is looking into the circumstances surrounding an injury to an elderly man.
The incident happened this past Sunday at the Boston Pizza on St. Laurent Boulevard around 11:45pm.
Reports indicate a 60-year-old man was making threats to restaurant staff, then had interactions with police both inside and out of the restaurant before being arrested.
He was then transported to hospital where he was diagnosed with a serious injury.
The S-I-U is asking anyone who may have witnessed these events to come forward.
Witnesses can call the lead investigator at 1-800-787-8529.