A day earlier, his stunned parents visited him as reports circulate that Markoff has told his brother that family members should forget about him because even more damning information has yet to be revealed.
Maria Cramer, a crime reporter at the Boston Globe, is at the center of the white-hot story.
"The case really began to take on a life of its own," she tells 48 Hours Mystery correspondent Peter Van Sant. "It's huge… you're talking about a very scary crime."
The story began on April 14, on the 20th floor of the Boston Marriott Copley Place hotel. A witness told 48 Hours Mystery she heard three "shrieks" and opened her door. A few feet away, a woman lay on the hallway carpet. Her head and shoulders were outside the room, and her long hair was splayed around her. The witness called security and watched as a guard moved the hair away from the woman's face. It was covered in blood.
"She was pronounced dead hours later at Boston Medical Center," says Cramer.
Detectives began to investigate the victim, Julissa Brisman, 25, of New York.
Says Cramer, "She was, I think… a young woman who was just trying to find herself, who'd had… tough years in her early 20s… she battled alcoholism. She was very open about that… she was really, you know, this sounds clichéd, but according to her friends, trying to turn her life around. She'd had it rough. And she had been supporting herself bartending and modeling, you know."
Brisman also marketed herself as an erotic masseuse, advertising her services on Craigslist - an extremely popular online bulletin board where virtually anything and everything is for sale.
"She would offer erotic massages that would probably, according to a friend, cross the line at a spa," Cramer explains.
Law enforcement sources told Cramer that Brisman's murderer was there not for a massage, but for money.
"He walked into the room, he took out the gun, and he tried to get her to go to the ground or tried to get her tied up," Cramer explains. "Julissa, according to authorities, fought back. She struggled with him as he tried to restrain her. And during the struggle, he hit her on the head hard, and then he shot her three times. One of the bullets struck her heart."
Police quickly checked security cameras in and around the hotel. Surveillance stills were taken just minutes after a witness called police. Investigators zero in on a tall, blond man who seems strangely unaffected - even calm.
"He looked like somebody who had just stepped out of the hotel bar where he'd been watching a game and downing a beer," says Cramer. "He didn't look like somebody who had committed murder or bound a woman and gagged her and robbed her of her money."
Trisha Leffler advertised her erotic services on Craigslist and is lucky to be alive. "I'm still shaking. I'm still nervous. His demeanor is very calm, like he'd done it before."
In an exclusive interview 48 Hours Leffler says she came face-to-face with the man shown on surveillance photos taken in a downtown Boston hotel just four days before Julissa Brisman was murdered.
"And we went into the room and as soon as I closed the door, he was standing behind me. And when I turned around, that's when he pulled the gun. I was a little nervous and immediately started shaking. My heart started beating fast. And he told me to lay down.
"He said if you be quiet, no harm will come to you. He put on black leather gloves and asked where my money was. He opened up my purse and immediately went after the money and put it in his pocket."
Leffler says the man took $800 in cash, and her credit cards. He then picked up her cell phone and erased his number from her call list. Tricia says he then tied her to the bathroom door, cut the telephone lines and taped her mouth.
"I got really scared. He was very calm. Polite. He didn't call me names or swear at me."
The man then left the room. Leffler says she managed to twist her way out of her restraints. She went to the room next door and called security.
"It dawned on me later that he could have killed me," she told 48 Hours. Police learn of a third assault at another hotel, this time in nearby Warwick, R.I. In surveillance pictures from the hotel, it again appears to be the same man as seen in Boston.
The M.O., says Cramer, is the same. "A woman who had advertised on Craigslist. She advertised lap dances."
The only difference this time is that the attacker is scared off by the woman's husband.
"Because it connected to Craigslist, everybody's imagination went wild," says Joe Moura, a Boston-based private investigator hired by 48 Hours Mystery. "He found what he thought was an easy target and that was going after prostitutes. Prostitutes, when they get robbed, don't call 911 and report a crime. It's a cost of doing business."
Behind the scenes, detectives catch a break. A friend of murder victim Julissa Brisman discovers a suspicious e-mail in her friend's account that appears to be from the killer, setting up their appointment on the night of her murder.
"That was a huge break in the investigation," says Moura. "Now they have an IP address. That was like leaving the gun at the scene with your fingerprints on the gun. It's the same exact thing."
Joe Caruso, CEO of Global Digital Forensics, says that the IP or Internet protocol address "is very much like a phone number" and can be traced from every e-mail.
"You can follow it just like you'd follow a footprint," he says. "Having that e-mail, the police on the job could have traced it back to a particular location."
Police were finally able to trace that computer IP address to an apartment building in Quincy, just outside of Boston. Investigators had a description of the suspect from one of the victims, plus prints of those black and white security camera photos. They began a stakeout.
On Sunday, April 19 - five days after Brisman's murder - police get their first look at Philip Markoff in person. He was with a woman.
"One sergeant basically called the investigators, after watching him all day, and said, 'I like him. I like him a lot,'" Cramer says.
Leffler makes a positive identification. It is now the afternoon of Monday, April 20.
"And that's when they come out carrying a small suitcase and an over-the- shoulder knapsack, get into the car, and start heading down Route 95 south," says Cramer.
The police take off after them.
"The police are now getting a little worried that maybe they're trying to flee the jurisdiction," Cramer continues. "So, they pull them over and say, 'Your car is being seized through a search warrant. We need you to come back to headquarters with us, and answer some questions.'"
Markoff calmly agrees to go downtown and asks for a lawyer. The woman with him is his fiancée, Megan McAllister. Cramer says McAllister begins asking a lot of questions, "Like anyone would. They proceed to tell her that her fiancé, Philip, is gonna be charged with murder. And she breaks down and cries."
Markoff, 23, was taken into custody and arrested for the murder of Julissa Brisman on April 14.
He is a suspect like no other second-year medical student at Boston University. His family and friends are astonished.
"His fiancée says, 'He wouldn't hurt a fly.' That he is 'a kind man. An intelligent, articulate man.' His stepfather said the same thing to us," Cramer says. "He said there must be some mistake. His grandfather, a lawyer, said the same thing… 'this is shocking.'"
Even more shocking is the evidence police found - a gun inside Markoff's Quincy apartment. It was inside a hollowed-out copy of the medical textbook "Gray's Anatomy."
"If they show that that gun was the gun that was involved in the shooting, you got a 'case closed' situation," says Maura. "See you later, he's gone."
Initial tests indicate the gun may be a match. The police also find what some claim are trophies from his victims - two pairs of panties, including one from Tricia Leffler. Police have also matched a fingerprint discovered at the Rhode Island crime scene to Markoff.
On Tuesday, April 21, Markoff was arraigned and charged with Brisman's murder and ordered held without bail. His lawyer says he is innocent.
Philip Markoff has not spoken publicly and remains an enigma.
"I would describe him as being the perfect all-American kid, you know what I mean," says Moura. "Perfect parents. Lovely girlfriend. Ready to get married. Going to med school… and I'm sure that… every parent would look at him and say, 'you know, I'm gonna have a son, I'd want one just like him.'"