By Katherine Q. Seelye and Ian Lovett, New York Times, April 26/27, 2013

BOSTON — Just five hours after the bombs exploded at the Boston Marathon last week, Dzhokhar Tsarnaev, 19, was back at his computer, doing what he did almost every day, posting a message on Twitter, “Ain’t no love in the heart of the city, stay safe people,” he wrote. His brother, Tamerlan, 26, returned to his home in Cambridge, which he shared with his wife and their 3-year-old daughter, and went about his normal activities, including a trip to the supermarket. [....]

Slipping back into a routine after committing a crime, even an atrocity, is fairly typical behavior, said Dr. Stuart W. Twemlow, a retired professor of psychology at Baylor College of Medicine in Houston. He works on threat assessment with the F.B.I. and helped on the Columbine shootings, among other cases.

A return to business as usual helps a criminal “blot out the horror with which he was associated,” Dr. Twemlow said. “That is a normal, dissociative response,” he said, adding that the younger brother, whose movements were more public, had most likely “denied and compartmentalized what he had just done.” [....]