BOSTON - Boston is marking one week since bombings near the marathon finish line killed three people and injured more than 180 others.

The city came to a standstill at 2:50 p.m. to remember the victims with a moment of silence at the exact time the first of two bombs exploded. Bells will ring across the city and state afterward.

Mourners will also spend the week saying final farewells to 29-year-old Krystle Campbell, 8-year-old Martin Richard and 23-year-old Lingzi Lu. The suspects are also suspected of killing MIT police officer Sean Collier and critically injuring transit officer Richard Donohue later in the week.

Authorities are meanwhile forging ahead with their investigation. The surviving suspect, 19-year-old Dzhokhar Tsarnaev, remains hospitalized and unable to speak with serious injuries, including a gunshot wound to the neck. He is still awaiting charges.

The suspect's brother, 26-year-old Tamerlan Tsarnaev, was killed Friday during a shootout with police in Watertown, Mass., a suburb of Boston that was shut down during the manhunt. Police say he was wounded and then run over by a car driven by his brother as he fled the gunfire. The medical examiner has not yet determined a cause of death.

Officials say the motive of the two ethnic Chechen brothers from southern Russia remains unclear. The city's police commissioner said that they had such a large cache of weapons that they were probably planning other attacks.

In Copley Square, cleanup has not yet finished at the crime scene. Police announced a five-phase plan to have the area reopened as soon as possible.