A massive manhunt for a suspect in Boston’s Marathon Day bombing forced authorities to place much of the city on lock-down, shuttering businesses including law firms plus federal and state courthouses as a frantic week drew to a frantic close.

Suspect Tamerlan Tsarnaev, 26, identified by authorities as one of two men pictured in surveillance photos released on Thursday afternoon, died in a shootout with police overnight, officials said. A transit police officer was wounded in that firefight and a police officer at the Massachusetts Institute of Technology was shot to death in a separate confrontation.

The other suspect, 19-year-old Dzhokhar Tsarnaev, remained at large as of mid-afternoon as officers went door-to-door in Watertown, Mass, a Boston suburb, looking for him.

Governor Deval Patrick directed Bostonians at around 8 a.m. to "shelter in place," but much of the city’s business was already on hold due to an earlier shutdown of the public transit system. Several heavily populated suburbs were already under sheltering orders.

Law firms reacted differently to the fast-moving crisis. "This morning, when these events were unfolding, we had a delayed opening," said Gina Addis, a spokeswoman at Boston’s Mintz, Levin, Cohn, Ferris, Glovsky and Popeo. "Some people had the option to come in and some people did come in.…No one was required to come in."

The fast-moving events began at about 10 a.m. Thursday night with a Cambridge, Mass., convenience store robbery, according to The Boston Globe. A short time later, the MIT officer was shot multiple times and later died. At about 10:30 p.m., two men carjacked a Mercedes SUV at gunpoint. Police said they shot Tamerlan Tsarnaev after he threw explosive devices at them. They separately detonated what they called two suspicious devices.

At Mintz Levin, Addis said, the firm officially closed the office at about 10:30 a.m. but that "people in the building have to stay," sustained by "plenty of food" that had been delivered for an early morning deal meeting.

From the Cambridge offices of intellectual property boutique Lando & Anastasi, partner John Anastasi said the first hint of trouble came overnight when a firm technology specialist—who holds a Ph.D. from MIT—received an email announcing the shooting of the school police officer.

"At 5 a.m., the conversations were going on amongst members of the firm about what was going on," Anastasi said. The firm notified employees at 6 a.m. that it was delaying the opening of the office, and decided at 8:45 a.m. to remain closed for the day, he said.

Duane Morris delayed its Boston office opening because of the public transit closure and decided at 10:30 to remain closed, said Boston managing partner Michael Gottfried via a BlackBerry message. "A couple of earlier-arrives were in," he said.

Ropes & Gray spokesman Tim Larimer said via email that the firm’s Boston office was open but "the vast majority of our lawyers and staff are working from home, where they are able to conduct business and handle any issues for our clients."

The Massachusetts State Court system closed courthouses in the affected area for the day, and officials at Boston’s John Joseph Moakley federal courthouse decided to close based on advice from law enforcement agencies.

Circuit executive Gary Wente said officials sent an automated message to court personnel and only a few judges and staffers were working in the building.

The Moakley courthouse closure forced the postponement of a key hearing in the trial of Boston mobster James "Whitey" Bulger.

Sheri Qualters can be contacted at squalters@alm.com.