Read more: Irish-born cop heads serial killer investigation

Read more: Craigslist killer death ends ordeal for his Irish fiancée

The remains of the four women found in Long Island, New York have been identified as Maureen Brainard-Barnes, Amber Lynn Costello, Megan Waterman and Melissa Barthelemy. Police believe the four women were killed by another 'Craigslist Killer.'

At least three of the women worked in the sex industry and used Craigslist to advertise their services according to Irishman Richard Dormer, the Suffolk County Police Commissioner.

Dormer said “I don't think it's a coincidence that four bodies just ended up in the same area."

Thomas Spota, Suffolk County’s District Attorney, speaking at a press conference said, “I believe it is, yes [a serial killer]. I think it fits within the definition of what a serial killer would be ... The causes of death appear to be substantially similar, but we're not going to go into any further aspect of that at this time."

The bodies were all dumped along a quarter-mile stretch at Gilgo Beach, on Fire Island, off Long Island, New York. It is believed that the bodies were dumped over an 18-month period.

The three women identified last week were Maureen Brainard-Barnes, 25, of Norwich, CT, Melissa Barthelemy, 24, of Erie County, NY, and Amber Lynn Costello, 27, of North Babylon, NY. The first body was identified as Megan Waterman, 22, of Maine.

Initially the police had not wished to pursue the theory that this was a serial killer; however, now they are sticking to their theory that this is a second 'Craigslist Killer.'

Spota also said that the murders do seem to all be linked to one suspect. “The whole pattern of young women utilizing the Internet to set up escort-prostitution jobs, and then they're all dumped in the same place ... It just lends itself to the serial killer theory, and that's what we're going on right now."

The police say they have some solid leads and their investigation is making rapid progress.