Waterloo Regional Police are investigating what they call a "suspicious" fatal car crash that happened in Kitchener early Sunday morning.

Police say a man was seen driving erratically on King Street around 1 a.m., before his car hit a curb and flipped over.

Emergency crews responded and transported the driver – the only person in the vehicle – to Grand River Hospital.

He later died of his injuries.

Police aren't specifying what type of injuries the man suffered, nor why they're treating the crash as suspicious.

"Our homicide investigators are leading the actual investigation, along with our forensic identification unit," says Staff Sgt. Shaena Morris with Waterloo Regional Police.

Hours after the crash, police canvassed Harold Avenue in Kitchener. They confirm it was in connection to the collision on King Street.

Neighbours say investigators went door-to-door, asking if anyone saw an "altercation" take place between 10:30 p.m. and 1 a.m.

"They just didn't tell us much of what happened," says Greg Euble, who lives on Harold Avenue. "Something happened last night and they wanted to know if he heard anything."

Like many other neighbours, Euble says it's usually a quiet street.

Police note the man's body was transported to a Hamilton hospital for a forensic post mortem.

His name has not yet been released.

Anyone with information is asked to call police or Crime Stoppers.