He's been indicted in connection with five more sexual assaults in Boston, where he grew up, the assaults dating back to 2007 and 2008.
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"Serial sexual offenders just don't stop assaulting because they get too much out of it. Both physically, psychologically, etc. And becomes an obsession," said Brad Garrett, ABC News Contributor, Former FBI Agent.
The 35-year-old, just weeks ago, was charged with seven other counts of rape and kidnapping for alleged attacks on four women during the same time period a decade-and-a-half ago.
He pleaded "not guilty" in the cases against him.
He was set free this month after his fiancé posted a half-a-million-dollar bond.
One of Nilo's alleged victims is outraged.
"I thought it was such a disappointment that they were just going to let him walk right out. These are such heinous crimes," Lori Pinkham said.
Before his arrest, authorities used genealogy websites to identify Nilo, later tracking him down at a corporate event, and matching DNA from a water glass to four of his alleged victims.
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Experts say with these new charges, prosecutors may have a stronger case to keep him behind bars.
"Going back and now having actual pictures of a suspect. They may well show other victims' photographs, perhaps in a photo lineup to determine they can actually pick them out," Garrett said.
Responding to the new charges, Nilo's attorney says his client "denies all the allegations...you can expect both a legal and factual challenge to the government's case."
Nilo is due in court next month.
Meanwhile, police in Madison, Wisconsin, where Nilo went to college, are now working with Boston police to see if any other cases could be connected to him.