Though his DNA has been linked to evidence at all three crime scenes, Rodriguez will not be charged until police have confirmation from a second DNA swab taken after his arrest.
The test results were not available Tuesday, but they are expected soon.
A review of records and interviews with neighbors and police sources show a young man who avoided run-ins with the law while growing up in a good home, but who drifted into drugs as he reached adulthood.
Despite those troubles - a few months in jail and a felony drug conviction - nothing in his background indicated an escalation into sexual violence.
Detectives interviewed two girlfriends - one former and one current - who said he was never violent and never displayed any sexual issues, sources said.
Rodriguez did not know any of the victims - Elaine Goldberg, 21, Nicole Piacentini, 35, or Casey Mahoney, 27. He told detectives that he had met each on the street in Kensington and propositioned them.
He described wanting to have "rough fantasy sex" that included choking them unconscious but said he did not set out to kill the women, according to sources.
After the first deaths, at least three other Kensington women came forward to report encounters with a man who sexually assaulted, choked, or hit them. They did not immediately report the attacks, so no DNA could be collected.
Two of the women described their attacker as soft-spoken; one said he had carried a white iPod and called himself "Anthony." One woman said she was choked and might have been sexually assaulted while she was unconscious.
Special Victims Unit detectives are investigating Rodriguez to see if he is responsible for those attacks and possibly others, said SVU Capt. John Darby.
