Boston marks somber second anniversary of marathon bombing

The city of Boston faces a somber day on Wednesday as it marks the second anniversary of the bombing attack on its marathon that killed three people and injured 264.

Mayor Martin Walsh plans to mark the day with a low-key ceremony at the site where twin pressure-cooker bombs went off on April 15, 2013, ripping through a crowd of some of the thousands of spectators, volunteers and athletes at the Boston Marathon.

"April 15 is a day that has come to stand for our deepest values," Walsh said. "I hope everyone can mark this day in a way that is appropriate and inclusive."

At 2:49 p.m. ET (1849 GMT) organizations around New England's largest city will observe a moment of silence to mark the time the first bomb went off.

The anniversary comes amid a break in the trial of Dzhokhar Tsarnaev, who was convicted last week of carrying out the bombing attack, before the same jury that found him guilty decides whether to sentence him to death or life in prison without possibility of parole.

Tsarnaev, 21, was the younger of two brothers who carried out the attack and three days later shot dead a police officer as they prepared to flee the city. His older brother, 26-year-old Tamerlan, died following a gunfight with police after that shooting.

Three people died in the bombing attack: 8-year-old Martin Richard; Chinese exchange student Lingzi Lu, 23; and restaurant manager Krystle Campbell, 29. Massachusetts Institute of Technology police officer Sean Collier, 26, was shot dead three days later.

Collier's sister earlier this week said on social media that she did not believe Tsarnaev, an ethnic Chechen who left a note suggesting the attack was an act of retribution for U.S. military campaigns in Muslim-dominated countries, deserved to die.

"Whenever someone speaks out against the death penalty, they are challenged to imagine how they would feel if someone they love were killed. I've been given that horrible perspective," Collier's sister, Jennifer Lemmerman, wrote on Facebook.

Other voices have been less forgiving, among them local CBS commentator Jon Keller, who had first argued against pursuing the death penalty, reasoning that allowing a guilty plea and life sentence would spare the cost of a trial.

"I changed my mind, and in the wake of the verdict I'm not hearing anything to change it again," Keller wrote earlier this month.