Less than a week after Andrew King moved to Cambridge, Mass., from Little Rock, Ark., the 26-year-old biostatistician found himself living under lockdown, along with a million or so others, as law enforcement hunted for Dzhokhar Tsarnaev, the surviving Boston Marathon bombing suspect.
With no cable hookup and his cell phone's Internet connection on the fritz, he found out about the lockdown from a friend in Atlanta.
"As soon as I read the text, I ran back in my room and literally covered my head with the sheets," he said. "It was terrifying."
For several hours, King huddled in his unpacked apartment that bordered where the suspect was eventually apprehended, peering out the window at the legions of armed police performing a slow sweep of the streets and driveways. King's friend kept texting him updated news reports, which King tried to reconcile with what he was seeing outside his door.
"It was just unbelievably surreal," he said.
Now that the subject has been apprehended, the city has no doubt breathed a collective sigh of relief. But a nagging sense of insecurity will likely linger for many, said experts.
"There is a particular sense of vulnerability to this act of violence, because these men lived among us. It is one of those traumatic events that are at the very heart of post traumatic stress," said Dr. Paul Ragan, an assistant professor of psychiatry at Vanderbilt University Medical Center in Nashville, Tenn.
After a traumatic five days that began with the marathon bombings and ended with the manhunt and lockdown, Ragan said he'd expect some percentage of Boston-area residents to experience some lingering level of anxiety, depression or fear.
Some will develop an "acute stress disorder," characterized by an emotional detachment, flashbacks, a heightened startle response, poor concentration and irritability, Ragan said. If such symptoms last for six months or longer, they could morph into full-blown post traumatic stress disorder.
"People think PTSD is a normal response to abnormal happenings, but that's not true," Ragan said. "It's classified as a severe anxiety disorder that requires treatment."
Ragan said he suspected the most deeply affected would continue to relive the events of the past week through nightmares, flashbacks and intrusive memories. He said they were also likely to develop a set of avoidance behaviors -- a marathoner might give up running, others might avoid Copley Square and other geographic reminders of the horrific events.
Although it is impossible to know how many people will be plagued by long-term psychological problems, Ragan said women, children and those with a genetic predisposition to psychological problems, including PTSD, or who lived through similar traumatic events, were at highest risk.
One of the biggest risk factors is proximity to the danger.