BOSTON - The fiancee of a Boston medical school student accused of fatally shooting a woman who placed an ad on Craigslist said police have the wrong man and there is no way he could have done it.

In an e-mail to ABC's "Good Morning America, Megan McAllister said Philip Markoff "could not hurt a fly." She called him "a beautiful person inside and out," according to the message read on the air today.

McAllister said she and Markoff expect to be married in August "and share a wonderful, meaningful life together."

Markoff, 22, was arrested in connection with the death of a woman last week who advertised massage services on Craigslist. Police have said he also could have been involved in other crimes against women who posted ads on Craigslist.

Two of Markoff's neighbors told "Good Morning America" today they were stunned by the accusations.

"I can't even put it into words, the disbelief I'm feeling right now," neighbor Jonathan Uva said. "This is a great guy ... Just a total disconnect from what we're hearing in the news."

Another neighbor, Mike Dye, said he seemed outgoing, but also rarely talked about himself.

Uva described "Just a nice, normal couple. I lived right next door to him, and I would never have expected this."

Police Monday arrested Markoff of Quincy in the woman's death last week at a luxury hotel. Markoff is to be arraigned today in Boston Municipal Court on charges of murder and unlawful possession of a firearm.