The motives behind the accused Craigslist Killer remain a mystery but police are eying gambling issues as a possible motive for accused Craigslist killer Philip Markoff’s alleged assaults on Boston-area escorts.

Markoff, 22, was held without bail on Tuesday for the murder of a Manhattan masseuse, Julissa Brisman, at the Copley Marriott hotel.

The second-year Boston University medical student lives with his fiance, who claims police have the wrong man.

He could not hurt a fly, Megan McAllister said in an e-mail to ABC's Good Morning America.All I have to say is Philip is a beautiful person, inside and out, she said in the e-mail read on Tuesday's program.

According to reports from Herald, Markoff was known to be a big gambler and investigators are probing whether money concerns tied to his gambling may have triggered the alleged violence spree.

Brisman, 26, was shot to death when she struggled with the killer in the doorway of her hotel room at the Marriott Copley Place hotel Tuesday night. Brisman was shot multiple times in the torso and police found a plastic restraint on one wrist.

The Craigslist killer calls women advertising services on the site, makes appointments to meet them at luxury hotels and then immediately ties them up and robs or kills them when he arrives.