Police in two states believe they are closing in on a suspect in the murder of a woman in a Boston hotel and attacks on women elsewhere in Boston and in Rhode Island who had advertised massage or erotic services on the Internet site Craigslist.
Investigators released today a clear photograph of the suspect taken during the most recent attack in Warwick, R.I. The series of images show the suspect inside the Holiday Inn Express Hotel last Thursday evening, the scene of an attempted robbery of a woman.
The pictures of the man in the Rhode Island hotel are very similar to a surveillance camera photo of the suspect in the murder of Julissa Brisman in a Boston hotel just days earlier.
Detectives also have a match among plastic zip-tie cuffs used to bind all three women. Two law enforcement sources told ABC News that the plastic restraints are being investigated after they were used to bind the hands of the victims.
"Detectives are aggressively pursuing a number of promising leads," police spokeswoman Elaine Driscoll told ABC News, refusing to comment on the plastic cuffs.
"Because of the active nature of the investigation, I cannot comment further," she said. "We could compromise the investigation by releasing information."
The sources told ABC News that they are "getting closer" to the arrest of the man captured on a series of surveillance cameras in Boston's upscale Back Bay: a 20-something, clean-cut blond man was seen leaving a luxury hotel where police said Brisman, a 26-year-old masseuse, was shot and killed just moments before in her room, police said.
Brisman's death is the second in a series of crimes against women who police say advertised on Craigslist.
The first crime happened Friday, April 10, at the Copley Square Westin hotel in Boston. Police say a woman, who had advertised exotic services on Craigslist, was held at gunpoint, bound and robbed of $800.
Then, on Tuesday night, April 14, Brisman was killed at the Marriott, just next door.
Finally, late Thursday night -- an hour south in Rhode Island -- there was a similar attempted robbery.
Police said all the women were tied up and threatened at gunpoint. It is believed that Brisman may have tried to resist her attacker as he tried to bind her wrists, and was shot.
Boston police are working with police in Rhode Island to determine if the cases are connected.
Former FBI agent and ABC News law enforcement expert Brad Garrett said Craigslist is a first choice for many looking for sexual services.
"By some sources, it's one of the leading avenues to promote prostitution because it's so easy," he said. "You place an ad, you say, 'Come to Hotel X, at a time and date' and a service is provided. It's really an ideal environment for criminals."
Earlier this year, New York radio anchor George Weber was murdered in his Brooklyn apartment, and police said they believe the killer answered Weber's Craigslist advertisement offering $60 for "rough sex." Weber was stabbed more than 50 times.
Gay Talese, an author who writes on the sex trade whose most popular book, "Thy Neighbor's Wife" came out long before sites like Craigslist existed, said such sites are making the problem much bigger because the players are anonymous.
"It's instant communication, it's instant sex, it's sometimes instantaneously a tragic situation," Talese said. "The reason it's definitely bigger is because any sense of caution or guilt associated with sexual interchange of a commercial nature is eliminated now."
Just last November, Craigslist entered into an agreement with 40 state attorneys general to eliminate some of the anonymity by requiring credit cards to post these erotic ads.
The company CEO told ABC News they are deeply saddened by the events and are "evaluating the incident to see if they can better protect Craigslist users."
But experts say little can be done to prevent criminals from using the Internet to stalk their prey.