It's about 12 hours after I last posted and essentially nothing happened until the last few minutes.  It looks as though the suspect is cornered in a boat in a driveway.  It is just outside the original 20 block perimenter in Watertown.  One answer to why they were fairly confident he was still here is that he was wounded in the original firefight.  Still, they were almost ready to give up the search in this area.

A tip from a woman who saw a ladder that was moved, blood on the tarp over the boat, and then helicopters got a heat signature--copters hadn't been able to fly most of the time because of low ceiling.

There were sounds of shots and now a report that there is a fire on the boat, which has gasoline aboard.  The general reporting is that this is coming to an end.

Also a detail: the order to stay in your homes in Watertown was carried by robocalls, so people in the middle of the night got a call.

The huge military/law enforcement presence seems to be now concerned that the suspect could still have a bomb, even a suicide bomb.  His older brother had a device strapped on him when he was shot.

I see there's some new information: the older brother was out of the country for six months last year.  There is a sister in New Jersey, who may have been bullied by the older brother.  The father is abroad.  The mother seems to be claiming this is all an FI plot.  Others are being questioned, roommates or former roommates of the suspect.

Flash bangs were thrown into the boat, to stun the suspect.  That might be the source of the fire.