A high-tech tip, an old-school stakeout in Craigslist attacks

Did he match the surveillance videos? Did he have the right kind of hair? The right physique? The same gait?

A few hours later, a tall, blond man with "wispy hair" emerged with a woman. He was awkward but athletic-looking. Like Celtics great Kevin McHale, one Boston sergeant said.

The police officers followed the couple as they drove away in their Toyota Corolla and soon found themselves at BJ's Wholesale Club. They watched from an unmarked car as the couple lugged cartons of water and other groceries to their Toyota and went back to their apartment.

They watched throughout the day, waiting and weighing the similarities. It looked like their guy. They picked up the phone.

"I like him," Sergeant Detective Brian Albert told the lead investigators in the case, who were awaiting word of the stakeout.

The call set in motion a series of events that led to the arrest 24 hours later of 23-year-old Philip Markoff, a Boston University medical student accused of terrorizing a woman who advertised erotic services through Craigslist and killing another who fought back, 26-year-old Julissa Brisman of New York.

Markoff, who is being held without bail, has pleaded not guilty to a charge of murder in Brissman's death at the Boston Marriott Copley Place April 14 and an attack on a prostitute at another posh downtown hotel four days earlier. He is also being eyed by Rhode Island authorities in the April 16 armed robbery of a Las Vegas prostitute in Warwick.

Yesterday Boston homicide investigators Lieutenant Detective Robert L. Merner and Sergeant Detective Daniel Duff provided a Globe reporter with new details of the six-day manhunt for the so-called Craigslist killer. They described the false leads, how Markoff was ultimately identified by a victim, his fiance's horrified reaction to the charges, and his own detached demeanor when police finally pulled him over on Interstate 95 Monday.

"He was very stoic, very quiet, never asked a question," Merner said.

A computer identification code known as an IP address was the first clue to draw police to the luxury towers in Quincy, where Markoff lived in a $1,400-a-month one-bedroom apartment.

That early break came on April 15 from a friend of Julissa Brisman, who was fatally shot at the Copley Marriott a day earlier. The friend, who asked the Globe to withhold her full name, said she looked at Brisman's e-mail account the morning she learned of her death and saw messages from a man Brisman was scheduled to see the night before for a massage. The friend immediately forwarded the e-mail to detectives.

Duff said that tip allowed them to "leapfrog" over myriad steps they would have had to take to track down Markoff.

But it would take them until Saturday to pinpoint the physical location of the computer used to send the e-mail or the name of the sender.

Until then, they chased more than 170 tips, some of them so strange they were put into a category Merner dubbed "completely crazy." One of them came from a 71-year-old Florida man who identified himself as a registered sex offender and told detectives, "I'm not sure it wasn't me who did it."

Others came from women convinced that their former boyfriend or former husband was the killer.

But there were stronger tips about men who resembled the suspect in the hotel surveillance photos. As police waited to find out where the IP address would lead them, they chased those other leads.

On Saturday night, after narrowing down the location through an Internet provider, police finally got a hit on the IP address, an apartment at 8 High Point Circle in Quincy.

When police saw Markoff, they were encouraged but needed more definitive proof he was their man, Duff said. The IP address, he said, could possibly have come from someone who had logged into Markoff's home Internet account from a remote location. And there could be other tall, blond men living at the building they had not seen yet.

"Everything we had up until that point was, yeah, he looks like the guy," Duff said. "We didn't want to jump to any conclusions, and so we couldn't just go down there and lock him based on, yes, he's 6-3 and blond."

Then on Monday a victim identified Markoff as the attacker, said Duff, who declined to say how the identification was made.

That afternoon members of the department's fugitive unit were outside the Quincy apartment building when they saw Markoff and his fiancée leave, carrying a small suitcase and an over-the-shoulder knapsack.

Fearing that the couple were trying to flee, police followed them and then made the arrest. When police pulled the couple over on I-95 in Walpole, they told them that the Corolla was being seized through a search warrant and that the couple needed to return with them to Boston for questioning.

At headquarters, Markoff remained calm, said nothing about the crimes, and told investigators he wanted a lawyer. The interrogation lasted less than 30 minutes.

But his fiancée, Megan McAllister, was nervous, confused, and full of questions. She told detectives she and Markoff were headed for an overnight trip to Foxwoods Casino in Connecticut, said Merner and Duff, who interviewed her.

When the men told her Markoff would be charged with murder, she broke down and cried.

McAllister told them she often stays in New Jersey with her parents, had been there most of the last week, and didn't return to Boston until Saturday. She had not been following the case of the so-called Craigslist killer, but recalled that her mother told her to be on guard.

" 'Be careful,' " Merner said McAllister's mother warned. " 'There was some guy that killed somebody up in Boston.' "

Merner said McAllister asked to use a computer to book a plane ticket back to New Jersey. Police drove her to Logan Airport that night. "She just wanted to go home," Duff said.

Maria Cramer can be reached at mcramer@globe.com.