An Ontario watchdog agency has begun investigating allegations that some Toronto police officers dragged a man into a parking lot and beat him to death.

The force's Special Investigations Unit (SIU) is reviewing videotape from a surveillance camera outside a 7-Eleven store, where 55-year-old Otto Vass died early Wednesday morning.

Witnesses claim that at least two officers attacked Vass, restraining him as he was punched and kicked.

The conduct of four police officers is now being investigated.

"He was beaten up like an animal for three to four minutes," Mir Hameed told CBC News. "More cops came down. But I think the guy was dead because he wasn't moving any more."

Neighbours said Vass, who was enjoying a late-night barbecue, had gone across the street for a bottle of pop. He never returned.

Otto Vass

It's believed he was escorted from the store by police, who had been responded to complaints about a man arguing with several younger people.

Exactly what happened in the parking lot is being looked into by the SIU, a civilian agency created 10 years ago. It probes possible wrongdoing by police officers that involves serious injury, death, or sexual assault.

On Thursday, investigators said they do not plan to release autopsy results until they've finished reviewing the case.