On Monday, 66-year-old Bruce McArthur was charged with three additional counts of first-degree murder after police discovered human remains in large planters at a Toronto property where the self-employed landscaper had worked.

Initially arrested on Jan. 18, and now charged in the deaths of five men, most of who were known to frequent Toronto’s gay village, the alleged serial killer may have had more victims, police say. The first-degree murder charges against McArthur have not been tested in court.

On Monday night, CTV Chief News Anchor and Senior Editor Lisa LaFlamme sat down with Mark Mendelson, a former detective with the Toronto Police Service who spent 14 years as a lead investigator with the homicide squad, to discuss the case.

These are some of the highlights of that interview:

ON THE POTENTIAL SCALE OF THE ALLEGED CRIMES
“My initial thoughts were, ‘There’s going to more,’” Mendelson said. “[The killer] … was organized and he had infiltrated that community and he sought out his victims. He did a very efficient job of disposing of these bodies, and slowly but surely, given what he has as an occupation, and access to earth-moving equipment and people’s homes and their backyards and everything else, it just seemed to me that this is not the end of this. We’ve got unidentified human remains that didn’t come back to the five victims that we know about now -- there’s going to be more.”

CRIMES OF PASSION OR STRATEGIC SLAUGHTER?
“A serial killer as we know it -- the Picktons, things of that nature… these are people that are organized,” Mendelson said. “They’ve thought out and methodically chosen their victims – recruited them, if you will, into their life. They’ve picked them because they’re vulnerable, they’re accessible. They generally don’t have a huge family connection around them, so if they go missing, it may take a while until somebody realizes that they’re missing… The disposal of the body is also preplanned – all of it is planned out – and that’s an organized killer.”

FOLLOWING THE INVESTIGATION FROM AFAR
“I can guarantee you that his computer and his smartphone were on all the time, and maybe watching the news all the time,” Mendelson said. “Because part of the thrill of doing all this is to watch how the police are going about their investigation and laughing at when they’re making mistakes or when they hear suggestions that they’re going in the wrong direction. It’s a bit of a game. It’s part of the thrill of this whole process for them… It makes him brazen and it makes him far more confident than he might have been had he thought that the police were onto him or somebody within the community.”

MACABRE MOTIVATIONS
“It’s the thrill of picking out the victim, it’s the thrill of planning out how you’re going to lure them in, it’s the thrill of the kill, and it’s the thrill of the forcible confinement when you have them,” Mendelson said. “And also the trophy, be it… video, pictures. It’s reliving it over and over again. So even though the body’s been disposed of, and they may have moved onto their next victim, they can always revisit that first kill.”

NOT LIKE THE REST OF US
“There’s certainly an element of mental illness there,” Mendelson said. “And there are people that are just outwardly and completely evil. I’ve met them, I’ve interviewed them in homicides, and they are cold -- they are cold-hearted. They have no soul and they just don’t care. They care about the thrill and the rush that they get from it.”