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鈥檚 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
鈥淢y initial thoughts were, 鈥楾here鈥檚 going to more,鈥欌�� Mendelson said. 鈥淸The killer] 鈥� 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鈥檚 homes and their backyards and everything else, it just seemed to me that this is not the end of this. We鈥檝e got unidentified human remains that didn鈥檛 come back to the five victims that we know about now -- there鈥檚 going to be more.鈥�

CRIMES OF PASSION OR STRATEGIC SLAUGHTER?
鈥淎 serial killer as we know it -- the Picktons, things of that nature鈥� these are people that are organized,鈥� Mendelson said. 鈥淭hey鈥檝e thought out and methodically chosen their victims 鈥� recruited them, if you will, into their life. They鈥檝e picked them because they鈥檙e vulnerable, they鈥檙e accessible. They generally don鈥檛 have a huge family connection around them, so if they go missing, it may take a while until somebody realizes that they鈥檙e missing鈥� The disposal of the body is also preplanned 鈥� all of it is planned out 鈥� and that鈥檚 an organized killer.鈥�

FOLLOWING THE INVESTIGATION FROM AFAR
鈥淚 can guarantee you that his computer and his smartphone were on all the time, and maybe watching the news all the time,鈥� Mendelson said. 鈥淏ecause part of the thrill of doing all this is to watch how the police are going about their investigation and laughing at when they鈥檙e making mistakes or when they hear suggestions that they鈥檙e going in the wrong direction. It鈥檚 a bit of a game. It鈥檚 part of the thrill of this whole process for them鈥� 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.鈥�

MACABRE MOTIVATIONS
鈥淚t鈥檚 the thrill of picking out the victim, it鈥檚 the thrill of planning out how you鈥檙e going to lure them in, it鈥檚 the thrill of the kill, and it鈥檚 the thrill of the forcible confinement when you have them,鈥� Mendelson said. 鈥淎nd also the trophy, be it鈥� video, pictures. It鈥檚 reliving it over and over again. So even though the body鈥檚 been disposed of, and they may have moved onto their next victim, they can always revisit that first kill.鈥�

NOT LIKE THE REST OF US
鈥淭here鈥檚 certainly an element of mental illness there,鈥� Mendelson said. 鈥淎nd there are people that are just outwardly and completely evil. I鈥檝e met them, I鈥檝e interviewed them in homicides, and they are cold -- they are cold-hearted. They have no soul and they just don鈥檛 care. They care about the thrill and the rush that they get from it.鈥�