A serial killer who has admitted eight murders was in the middle of another killing when police knocked on his door, a court has heard.
Police, who had been monitoring the 67-year-old landscape gardener as a potential suspect, moved in for fears another murder was about to take place.
When they arrived, they found McArthur had chained the man – identified in court only as John – to a four-poster bed and placed a black bag over his head.
He was taping his victim’s mouth shut at the moment police knocked.
The horrifying revelation was among a number of gruesome details which came to light on the first day of the serial killer’s sentencing on Monday.
The evidence offered was so disturbing that prosecutor Michael Cantlon took the unusual of step of warning those present it could affect their mental health.
"Ask yourself if you need to be here," he said.
McArthur has admitted killing Dean Lisowick, Soroush Mahmudi, Skandaraj Navaratnam, Selim Esen, Andrew Kinsman, Majeed Kayhan, Abdulbasir Faizi and Kirushna Kanagaratnam between 2010 and 2017.
The majority of his victims were immigrants from South Asia or the Middle East who frequented – either openly or secretly – Toronto’s gay village.
Photos taken from McArthur's computer revealed that he posed many of his dead victims in fur coats and hats. Several had unlit cigars hanging from their mouths. One had his eyes taped open.
McArthur shaved some of his victims' heads and beards after strangling them, and kept their hair in bags at a shed near a city cemetery.
Other body parts were dumped in plant pots at the suburban home of one of his gardening clients.
The big break in the case came last summer after McArthur killed Andrew Kinsman.
The 49-year-old victim had an entry in his diary marked "Bruce" for the day he vanished.
Video surveillance footage traced by police showed him getting into a car that was traced back to McArthur.
With evidence apparently limited to these two key facts, officers chose to keep their suspect under surveillance, even covertly searching his apartment.
But it was only when they realised John – who McArthur met on a gay dating app – had gone back to the apartment that officers moved in.
A USB device they confiscated from McArthur’s home during the following investigation was found to have folders containing several of his victims names. Ominously, the final folder was named after the man police rescued.
The court also heard that there may have been at least two previous chances to stop McArthur.
In 2013, he was interviewed as part of the police investigation into the disappearances of Navaratnam, Faizi and Kayhan – but, as a long-time friend of Navaratnam, police treated him as a witness rather than a suspect.
Then in 2016, he was interviewed about an unrelated matter after trying to strangle a friend.
McArthur had invited the unidentified man into his van for casual sex, and asked him to lie in the back on top of a fur coat. As he did so, McArthur - who left his family after coming out in his 40s - grabbed his wrist and started to strangle him.
Although the friend managed to escape and reported the incident, McArthur was not charged because police found his version of events – a domestic argument – credible.
They did not apparently place any significance on the fact tMcArthur’s van had been lined with plastic.
Sentencing will now take place on Wednesday, but it is almost certain he will be locked up for the rest of his life.