"[The killer] could be law enforcement, could be a civil servant, could be a code enforcement person, could be a building inspector, could be a postman ... or it could be anyone who knows the area quite well," former New York Police Department detective Wally Zeins told ABC News.
Police are also looking at people who have had regular or routine access to the beach where the bodies were found, and investigators are also exploring possible links to the serial killer who murdered prostitutes in New Jersey, they said.
According to one investigator familiar with the case and the behavior of serial killers, this appears to be an organized serial killer who plans methodically and is probably above average intelligence. It appears that the killer usually lures people, kills them in one place and then disposes of the body in another.
This sort of killer is often social -- not a loner -- with family, friends and what would appear to be a normal life, the investigator said.
Zeins is confident that the killer will eventually slip up.
"Whoever it is will make a mistake, and they'll get caught," he said.