Court heard police had arrested McArthur in 2016 for assault for choking a man in the back of his van.
The men he killed between 2010 and 2017 all had ties to the city's gay community and shared social traits that put them at greater risk of harm, Cantlon said.
McArthur has pleaded guilty to killing Selim Esen, 44, Andrew Kinsman, 49, Majeed Kayhan, 58, Dean Lisowick, 47, Soroush Mahmudi, 50, Skandaraj Navaratnam, 40, Abdulbasir Faizi, 42, and Kirushna Kanagaratnam, 37.
The victims fit a pattern: Most were of Middle Eastern or South Asian descent and lived on the margins of Canadian society.
"For years, members of the LGBT community in Toronto believed they were being targeted by a killer", Cantlon said. The Globe has previously reported that in 2016, Mr. McArthur was interviewed by police after a man said Mr. McArthur choked him during sex.
A serial killer played dress-up with his victims after he had murdered them.
Surveillance footage of Kinsman entering a van linked to McArthur helped police narrow down a suspect.
A Dodge dealership worker told police it was a 2004 Dodge Caravan and when they requested information from Ontario's Ministry of Transportation, they received a list of 6,181 red such vehicles made between 2003 and 2006.
McArthur was the only one who owned the 2004 model, the only one whose vehicle had chrome siding and lacked fog lights, and the only one Toronto police had recently brought in for an interview - an encounter in June 2016 during which McArthur, under arrest for assault but never charged, told his questioners where he lived.
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However, Turkey's Islamist president, Recep Erdogan, called the demand "a very serious mistake" and flatly told U.S. The report said that when US troops withdraw, it is "unclear what would occur with the Manbij agreement".
McArthur, 67, was arrested in January 2018 in connection with a police investigation of missing men in Toronto's Gay Village neighborhood, and was charged with the murders of five men in a case that shook Toronto's gay community. They later uncovered the folder bearing John's name and containing his photos alongside other folders filled with evidence of McArthur's previous killings. His beard was shaved off in a few photos. The presence of a rope and pipe signified that he had restrained and strangled some of the men. Many of their remains were found buried in potted planters of a home he worked on as a landscaper or buried in a ravine next to the property.
Toronto police released a statement stating, "When Homicide Squad investigators working the Bruce McArthur case identified prior investigative concerns, they immediately contacted Professional Standards". On that day, "John" recalled McArthur asking him if his family knew where he was going, to which he responded that their meeting was a "secret".
Cantlon has said the cases ranging from 2010 to 2017 involved sexual assault or forcible confinement and said the bodies were hidden and dismembered.
First degree murder carries a sentence of life in prison with parole possible after 25 years served.
On the first day of what is expected to be approximately a three-day hearing, McArthur sat motionless, looking straight ahead, as Crown prosecutor Michael Cantlon detailed the ways the murderer tried, and failed, to cover his tracks, destroy evidence of his crimes and evade arrest. The latter option would bar him from seeking parole for 200 years.
On Monday, the court heard the gruesome details of McArthur's "planned and deliberate" murders - including his "post-offence rituals" such as photography, staging the bodies and keeping items.
A woman speaking on behalf of the Esen family had harsh words for McArthur and police. Kinsman was endearingly grumpy, loved to bake banana bread and cared for his neighbour Meaghan Marian's birds for months when she was working overseas.
Cantlon said police observing McArthur saw him bring John up to his apartment and chose to move quickly given the "exigent circumstances".