TORONTO - Ontario's ombudsman is criticizing the province's police watchdog over the conduct of investigators probing a fatal police shooting.

Andre Marin says the Special Investigations Unit must take decisive action to ensure the credibility of the agency.

This after a French TV documentary raised questions about the February shooting of Michael Eligon of Toronto.

Marin watched the documentary and says he was "astounded" when it showed an SIU forensic investigator wearing what appears to be a police ring.

Marin says he also noticed two investigators offering excuses about why the officer discharged his firearm -- which he says is an example of "tunnel vision."

The SIU says it has suspended one forensic investigator for wearing the police ring and disciplined two others for comments made to the media.

The wearing of the ring was described as a "very serious transgression" by SIU director Ian Scott, who said he suspended the investigator within 24 hours of learning about it.

"We have a policy in place that clearly states investigators are not to wear police insignia, as it could give the appearance of pro-police bias," Scott said in a statement Friday.

"It is imperative we always be seen as independent from the police."

As for the investigators who spoke to media about police self-defence, Scott called their comments inappropriate.

Marin, who authored a report critical of the SIU in 2008, said he was seeing the same problems again four years later. He called the wearing of paraphernalia such as the ring "preposterous."

"The director of the SIU has to take decisive action right now ... and nip this one in the bud," he said, adding Scott has so far reacted properly by quickly denouncing such incidents and taking disciplinary action.

But he said he wonders if the latest incident is just the "tip of the iceberg" and more needs to be done.

"The credibility of the unit hinges upon its ability to conduct independent, impartial investigation," said Marin.

"If you show up to the scene and you look like a police groupie, you won't have any credibility in your findings."

The SIU has cleared the officer who shot Eligon after the 29-year-old escaped from Toronto East General Hospital. Eligon was armed with scissors and dressed in a hospital gown.

A coroner's inquest has been launched into his death, which has raised concerns about how police are trained to handle people with mental illness.

Scott said the SIU's investigation was thorough.

"There was enough information through the in-car camera video, ballistics, civilian and police interviews that I am satisfied that there was a sufficient factual basis to make an informed decision about police liability," Scott said.

The SIU was created in 1990 to investigate cases involving police where there has been death, serious injury or allegations of sexual assault.