Boston manhunt: Fear factor hits hiding Watertown residents
I arrived at Watertown around four in the morning and watched as America poured its mighty forces into this small suburb in search of one man, the murderer behind the Boston bombings.
Around 20 armoured cars thundered into town. A few minutes later twice that number of police cars, blue lights flashing. Then a phalanx of motorcycles.
Most of the people going in were police, but they looked just like troops going to war - in camouflage, with steel helmets, clutching automatic rifles at the ready.
Later in the day black hawk helicopters circled over head.
All day inside the cordon, police have been going from house to house, door to door, checking that people are safe, looking for the killer.
It wasn't surprising that police told everyone to stay off the streets, and stay indoors.
What was surprising was that they later closed down the whole city - public transport shut down, businesses were told not to open. The advice to all of the millions of inhabitants of greater Boston was "shelter in place, lock your doors".
Better scared than hurt
It has turned some into refugees for the day.
A man and his 17-year-old daughter wander around the small shopping centre, now filled with TV trucks and journalists. She's clutching a puppy and is still dressed in pyjamas.
They'd gone out late at night to pick up their new pet and when they came back they were told by police they couldn't return to their home in Watertown - there was a terrorist on the loose, with explosives.
We and they are on one side of the cordon. Inside those 20 blocks it must be terrifying: to be told to stay inside, behind a locked door, frightened that an armed killer - perhaps wearing a suicide vest - could turn up on your door step.
And just about everyone in Boston, shut at home, will have that thought. Imagine it in your own home city, or town, or village.
The police obviously don't want to create panic but they have. They would rather get their man, and they prefer that people are frightened than hurt.
America wasn't cowed by the bombings, but having one of its oldest cities shut down may have a greater impact.
At the start of the week, a teenager and his brother brought the carnage of terror to the streets of America for the first time since 9/11.
By the end of the week, he had paralysed the whole area, doubtless causing millions of dollars worth of economic damage and forcing millions to cower at home, in fear.
I don't think America will feel normal again until he's caught.