Philip Markoff, suspected 'Craigslist Killer' and med student, in custody

Boston police released this video surveillance photo. Police believe this is Phillip Markoff, suspected of killing a masseuse-for-hire at the Marriott Copley Hotel.

Boston police suspect a 22-year-old med student who is engaged to be married is the "Craigslist Killer" who murdered a New York masseuse and attacked at least two other escorts, according to The New York Daily News.

Philip Markoff, a Boston University student, will be arraigned on murder charges today for the death of Julissa Brisman, 26. Police believe Markoff, who has no prior record, has preyed on sex workers for some time.

Brisman, who advertised her services on Craigslist, was shot in a Boston hotel last Tuesday. Markoff also faces charges of kidnapping and robbing an exotic dancer, who also advertised online. Police also are probing Markoff's connection to the armed robbery of a Las Vegas prostitute in a Rhode Island hotel, The New York Daily News reports.

Markoff is engaged to marry Megan McAllister, a fellow med student. She defended him this morning in an e-mail sent to ABC News.

"Unfortunately, you were given wrong information as was the public," McAllister writes to ABC News in an e-mail. "All I have to say to you is Philip is a beautiful person inside and out and could not hurt a fly! A police officer in Boston (or many) is trying to make big bucks by selling this false story to the TV stations. What else is new?? Philip is an intelligent man who is just trying to live his life so if you could leave us alone we would greatly appreciate it. We expect to marry in August and share a wonderful, meaningful life together."
Police stopped Markoff at 4 p.m. Monday on Interstate 95 south of Boston. Earlier in the day, police released security photos showing Markoff strolling to and from the three crime scenes peering at his BlackBerry. Police believe his motive in the crimes was to pay off gambling debts, according to the ABC News report.