Kathleen O'Donnell spotted William Ellery Channing sporting some new shades this morning at his usual perch at the Public Garden entrance at Arlington and Boylston streets.

JB Parrett photographed a homeless man on the steps of Arlington Street Church yesterday.

BFD response to mystery boom. Photo by Victoria Bedford.

Around 8:50 p.m., Boston firefighters and Transit Police rushed to the area of Arlington and Boylston streets after several people reported hearing a loud explosion. Cara Terez, sitting on the Rattlesnake roof deck, tweeted:

Loud LOUD explosion.

As a precaution, the T shut Green Line service as firefighters looked around on the street and in the station for the source of the boom, but they found nothing, an inbound Green Line driver reported the tunnel between Copley and Arlington was fine and service started up about 10 minutes later.

Brian D'Amico tweets police speculate a tour bus may have had an engine backfire or two.

Bostonians had their choice of venues for standing around this AM, such as Andrew. Photo by Chris Wright.

Fire on the inbound tracks between Arlington and Copley around 7:40, Jay Joynes tweets. At first, the T shut Arlington station because of heavy smoke, but shortly after 8 a.m., it shut down all Green Line service downtown. And shortly after 8:30, the T began evacuating trolleys stuck in the tunnel near Hynes and Copley stations.

The T eventually sent in some shuttle buses between stations to the west and downtown, but many commuters didn't wait. As Gracetopia tweets:

I now feel like one of the army of the commute, as I walk from Kenmore to downtown with my fellow MBTA refugees.

Lindsay Douglas, though, was one of the people who stayed behind at Kenmore:

I've never seen chaos like this. Coldest day of the year + the MBTA shuts down the green line. Yelling+angry people.

And because misery loves company, an inbound Red Line train died not long after at Charles/MGH, Rob Grover tweets. Later, another train died at Porter. Around 9:20, another train died, inbound at Andrew.

Jesse Haley noticed this hawk perched at Boylston and Arlington this morning, "attracting tourists and scattering squirrels."

MBTA Transit Police report the first arrest of the year for a smartphone theft, off a woman on a Green Line trolley at Arlington Street station yesterday afternoon.

According to a Transit Police report, Emmanuel Castro, 17, of Roxbury, grabbed an iPhone right out of a woman's hands when their inbound trolley stopped at Arlington around 2 p.m. Police say the woman chased after him from the train and then up the stairs to the street, where where she lost him. But an unidentified man, spotting the two running, figured out what was going on and began chasing Castro himself, calling police as they ran all the way to Fairfield and Beacon streets.

Police say they caught up with Castro at Fairfield and Comm. Ave. where, on a pat frisk, an officer felt something hard and pulled an Apple iPhone 4G in Castro's right front pocket. The officer then called one of the numbers on the phone and was, police say, connected to the woman's aunt.

Castro was charged with unarmed robbery.

Innocent, etc.

Boston Fire Department is on scene for a trolley fire on the outbound side. Pantograph fire is out, the train is dead, expect delays.