Thousands of Britons have been caught up in the lockdown of Boston as authorities continue their search for the surviving suspect in the marathon bombing.
Rob Ledniczky, a first-year history student at Harvard University, said streets were deserted in Cambridge as residents were ordered to stay indoors.
The 19-year-old, from Maidstone, in Kent, said: "It's a pretty weird atmosphere. It's a surreal experience that this is happening right outside our windows. Everyone's in a state of shock.
"We've been instructed by the university that our classes have been cancelled and to stay indoors.
"The campus is completely deserted and when I look out at Cambridge itself, the usually busy streets are empty."
Mr Ledniczky said he was on campus on Thursday night when reports emerged of the shooting at the Massachusetts Institute of Technology (MIT).
"About 30 or 40 police cars screeched past. Work ground to a halt and people were watching the news to keep up to date," he added.
An estimated 17,400 UK-born citizens live in the Greater Boston area, according to the US Census Bureau.
There are also some 11,900 Irish-born residents in the population of more than 4.5 million, a bureau spokesman said.
Around a quarter of all Boston residents claim Irish heritage, he added.