(CNN) A serial killer who preyed on men before burying their bodies in potted plants pleaded guilty to eight counts of first-degree murder Tuesday.

Landscaper Bruce McArthur, 67, was first arrested last January when he was charged with the murder of two men who had gone missing in 2017. Since then, police have investigated locations around Toronto where McArthur worked as a landscaper. The investigation led to murder charrge after murder charge.

McArthur pleaded guilty Tuesday to killing Selim Esen, Andrew Kinsman, Majeed Kayhan, Dean Lisowick, Soroush Mahmudi, Skandaraj Navaratnam, Abdulbasir Faizi, and Kirushna Kanagaratnam.

"It's a serial killer -- alleged serial killer," homicide detective Sgt. Hank Idsinga said last year. "The city of Toronto has never seen anything like this. The resources that are being thrown at it, everything that we have. I'd call it an unprecedented type of investigation."

McArthur's sentencing hearing is scheduled for Monday at 10 a.m. ET. Victim impact statements from the families of the dead men are also expected.

No clear motive

"We, myself and the investigative team, are pleased that Mr. McArthur has pled guilty today, sparing the community and those who knew the victims a lengthy trial," Toronto Police Detective David Dickinson said. "I believe that this is the best possible outcome for the families and the community."

Dickinson said he did not of any clear motive in the killings.

"I don't know if we'll ever know why," Dickinson said.

Many of the victims, although not all, were from the Gay Village, a neighborhood in Toronto known for its predominantly gay population. McArthur had some sort of relationship with each of his victims, some of which were sexual, Toronto Police spokeswoman Meaghan Gray said last year.

Haran Vijayanathan, executive director of Alliance for South Asian AIDS Prevention said the guilty pleas were important for getting closure in the case.

"It's actually quite relieving I think, because we have an answer now, and he's pled guilty, and that puts the community and the family at rest to say that we have closure now, finally," he said.

Paul Ciantar, 54, told CNN last year that he had seen McArthur in the Gay Village area, but didn't know him personally. Ciantar said he has friends who did know McArthur and added, "They all said that they never would have suspected him."

"He looks like Santa Claus. He looks harmless. That probably really helped him," Ciantar added.

Indeed, McArthur actually did work as a Santa Claus at a mall in Scarborough, Ontario, over the past few Christmas seasons, according to Agincourt Mall.

Gary Speedie was a former coworker of McArthur. The two met while doing landscape work for a mutual friend.

"He was always opinionated," Speedie told CNN. "Never got any warm, friendly vibes from him. He seemed moody. Usually fairly happy, but sometimes quiet."