Police, using a search warrant following Markoff's arrest, also found underwear and other items belonging to victims, along with a handgun hidden in a copy of the medical textbook "Gray's Anatomy," sources tell CBS station WBZ.
The Boston University medical student is accused of stalking two women who advertised erotic acts through Craigslist - robbing one and killing Brisman.
That gun is a preliminary match to the gun used in Brisman's murder, WBZ reports.
On Thursday, prosecutors placed an ad on Craigslist Thursday in an attempt to find other women who may have been victimized by Markoff.
Suffolk County District Attorney's Office spokesman Jake Wark said that Boston investigators hope the ad, posted in the "erotic services" section of the Web site, will persuade other possible victims to come forth.
"Were you attacked or robbed at a Boston-area hotel after placing an ad on Craigslist?" the ad asked. "If so, you may have information that could aid the investigation into the April 10 armed robbery of a woman at the Westin Copley Place Hotel and the April 14 murder of a woman at the Marriott Copley Place Hotel. Both victims were attacked by a prospective client who had contacted them through ads placed on Craigslist."
Also Thursday, a law enforcement official, speaking to The Associated Press on the condition of anonymity because he was not authorized to discuss the case, said Markoff had been placed on suicide watch at the Boston jail where he is being held. ABC News and The Boston Globe, citing unidentified law enforcement sources, reported that what appeared to be shoelace marks were found on his neck.
Defense attorney John Salsberg told reporters he was concerned about Markoff's well-being but otherwise declined to comment on the reports.
Jail officials declined to comment to The Associated Press, citing privacy rules.
In an exclusive interview with the New York Daily News, a college friend of alleged "Craigslist Killer" Philip Markoff discussed an incident with him four years ago - possibly fueled by alcohol - which may have provided a glimpse into the medical student's dark side, reports CBS News correspondent Daniel Sieberg.
"He pushed me up against the wall and tried kissing me," Morgan Houston told the paper in the videotaped interview, obtained exclusively by CBS News.
"I couldn't physically get him off of me," Houston told the paper.
Since Markoff's arrest, his fiancée, Megan McAllister, has not spoken publicly. Thursday, her father spoke for her, reports CBS News correspondent Bianca Solorzano.
"She's got a lot of friends, lot of family friends its been a big help to us, everybody has been wonderful," James McAllister said.
McAllister, who still plans to marry Markoff this summer, has been holed up at her family's new jersey home since his arrest. According to her father, Megan believes police have the wrong man.
"She is still confident in Phil," he said.
And she's not the only one. Markoff supporters started a Facebook site called "Phil Markoff is innocent until proven guilty."