Boston Mourns MIT Officer's Death

Vice President Joe Biden, law enforcement officials, and MIT students, faculty and staff, joined more than 4,000 mourners Wednesday to remember a murdered MIT campus police officer.

Authorities said Mark Collier was gunned down by Dzhokhar and Tamerlan Tsarnev three days after the Boston Marathon bombing that rocked the city and capitvated the nation's attention.

The line of mourners stretched for nearly half of a mile, a stretch fortified with tight security, including metal detectors and bomb-sniffing dogs.

The funeral Wednesday marks a further stage of Boston's coming to terms with the marathon bombings nine days ago. Although the pace of life has resumed after last week's manhunt for suspects Dzhokhar and Tamerlan Tsarnaev - a manhunt that paralyzed the city and forced residents to remain in-doors - residents said the grieving process will be a long one.

"I don't think there's going to be a sense of normalcy for a while," Tom Champoux, a Boston resident, said. "There are scars here that will be with us for a long time."

Suspect Dzhokhar Tsarnaev, 19, is still recoverying from wounds suffered during the manhunt last week, and he could face the death penalty if found guilty of plotting murder using a weapon of mass destruction.

His 26-year-old brother and alleged accomplice, Tamerlan Tsarnaev, died in a shootout last week.

The Massachusetts Office of the Chief Medical Examiner spokesperson said that Tamerlan Tsarnaev's body is still in the medical examiner's custody.

The parents of the two suspects, Anzor Tsarnev and Zubeidat Tsarnaeva, plan to fly to the U.S. Thursday to bring Tamerlan Tsarnaev's body back to Russia.

U.S. investigators are still investigating what motivated the Tsarnaev brothers. According to officials, the explosions were triggered by remote-controlled detonators. 

The Associated Press contributed to this report.