BOSTON — He favors khaki pants and oxford shirts, graduated summa cum laude from college and proposed to his fiancee on the beach in Maine. But Philip Markoff, a tall, blond medical student who registered for wedding gifts at Pottery Barn, is also a brutal predator, prosecutors said Tuesday.

“Philip Markoff is a man who is willing to take advantage of women, to hurt them, to beat them, to rob them,” said Daniel Conley, the Suffolk County District Attorney, after Markoff, 22, pleaded not guilty in Boston Municipal Court. “He thought he was going to get away with it; he thought he was too smart for us.”

But if Markoff did kill Julianna Brisman, a masseuse and aspiring model with whom he supposedly arranged an appointment through Craigslist early last week, he did a poor job of covering his tracks.

Conley said investigators discovered a semi-automatic handgun, ammunition, duct tape and plastic zip ties at Markoff’s apartment in Quincy, just south of Boston. The plastic ties were the same kind used to bind the hands of Brisman on April 14, he said, and of a second masseuse Markoff is charged with robbing at gunpoint.

Building a case

Friends described Markoff as an industrious student who had always excelled, but who also had a weakness for gambling and hanging out in bars. He was on his way to Foxwoods Resort Casino with his fiancee and $1,000 in cash when he was arrested.

Both attacks took place at hotels in Boston’s Back Bay neighborhood, a popular destination for tourists and business travelers. And security cameras captured a tall, blond man leaving both hotels shortly after the attacks took place, peering coolly at his cell phone as he strode out.

The police used records from that cell phone account to track down Markoff, as well as an IP address that led them to his home in Quincy.

“They begin to put the house under surveillance,” Conley said, “they see Philip Markoff, he matches the description quite remarkably, and again the case just begins to build from that point.”

Markoff’s supporters

“Philip Markoff is not guilty of the charges,” his lawyer, John Salsberg, said outside the courthouse Tuesday. He also said Markoff had “his family’s support.”

But no relatives were present for Markoff’s arraignment, at which he appeared in khakis and a rumpled oxford shirt, staring glumly ahead with his hands cuffed at his waist.

In the hours before the court proceeding, Markoff’s fiancee, Megan McAllister, reached out to several television networks to proclaim his innocence.

According to ABC’s “Good Morning America,” McAllister sent the show an e-mail describing Markoff as “a beautiful person inside and out” who “could not hurt a fly.”