Markoff is charged with Brisman's murder and the robbery of a second woman in Boston. He is also expected to be charged with the robbery of a third woman at a Rhode Island hotel. That woman had also advertised erotic services on Craigslist.
A law enforcement source close to the investigation told ABC News that officers recovered a semi-automatic handgun and panties belonging to Brisman in the Quincy, Mass., apartment Markoff shared with his fiancee. The gun and panties were hidden in a copy of the popular medical school textbook "Gray's Anatomy."
The gun found inside Markoff's apartment is a forensic match to casings on bullets used to shoot and kill Brisman, ABC News has learned.
In addition, investigators said the plastic restraining ties used in an attack at a Holiday Inn Express in Warwick, R.I., -- on a woman who had advertised "erotic services" -- exactly match plastic ties found in Markoff's apartment.
Warwick Police Chief Col. Steve McCartney told ABC News last week that the woman who was robbed in the Holiday Inn Express was reluctant to cooperate with the investigation.