Idsinga declined to say how police obtained the picture of the dead man.
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He said they showed the picture to members of the gay community but could not identify him. Many of the other alleged victims have been darker skinned and of South Asian or Middle Eastern descent who frequented the "Gay Village" area of Toronto.
Idsinga said they've now found the dismembered remains of at least seven individuals this year in large planters at a home where McArthur did landscaping work and stored objects. It's not clear if the remains of the seventh man are of the same man seen in the picture released by police.
He said they realize how difficult it might be for a relative or friend to see the picture and realize the man is deceased.
"I've never done this before," he said about releasing the photo. "I do it with great hesitation. It is obviously a key piece of evidence that we have that we are releasing, but we feel by releasing it, hopefully we can identify him and close off that area of the investigation."
Investigators have identified three sets of remains so far — 49-year-old Andrew Kinsman, 50-year-old Soroush Mahmudi and 40-year-old Skandaraj Navaratnam.
McArthur, 66, is charged with first-degree murder in their deaths, as well as the presumed deaths of 44-year-old Selim Esen; Majeed Kayhan, 58; and Dean Lisowick, either 43 or 44. Police have said they believe there are more victims.
Dr. Michael Pollanen, Chief Forensic Pathologist for the Province of Ontario, said the causes of death are pending further studies.
Investigators have not yet released complete details, but McArthur is believed to have met his alleged victims in the Gay Village and on gay dating apps for older and large men with names such as "SilverDaddies" and "Bear411."
Police are looking at unsolved missing person cases to determine if there are connections to McArthur and are running down tips that have come in from around the world.
McArthur, a grandfather and former mall Santa Claus, has not entered a plea. His case is due back in court March 14. Edward Royle, a lawyer for McArthur, has previously declined to comment on the case and didn't respond to a message seeking comment on Monday.