Fallen campus police Officer Sean Collier, 27, was honored at a memorial service at MIT’s Briggs Field in Cambridge. Thousands of Massachusetts Institute of Technology students, faculty, and staff, as well as law enforcement officials from across the nation, attended. Vice President Joe Biden, MIT President L. Rafael Reif, MIT Police Chief John DiFava, and members of Collier’s family spoke.

Photos: Slain MIT officer laid to rest

Vice President Joe Biden gave a moving speech.

A Massachusetts State trooper saluted during the service.

MIT police pallbearers carried Sean Collier’s casket.

Alex Flores (right) reflected the mood at MIT.

A police officer left the memorial with a program.

The police line head to Briggs Field.

MIT employee Jennifer Earls paid her respects at the make-shift memorial for Collier outside of the college's Stata Center.

Robert Rogers (left) puts his hand on his stepbrother, Andrew Collier, after delivering the eulogy.

A woman held a sign reading "No More Hurting People, Peace.”

Thousands of mourners attended the memorial service at Briggs Field in Cambridge.

“I hope you find some solace in this moment of extreme grief...no child should pre-decease their parents,” Biden said to family.

A casket was stood over by a Massachusetts Institute of Technology honor guard during the memorial service.

James Taylor sang “The Water is Wide” and “Shower the People” at the memorial service.

Mourners bowed their heads during a memorial service for Officer Sean Collier.

Police officers lined up outside Briggs Field on April 24.

James Taylor warmed up before the memorial service for Officer Sean Collier.

Members of the Massachusetts Institute of Technology community arrived for a memorial service. Officer Sean Collier was allegedly killed by the brothers accused of the Boston Marathon bombings, Dzhokhar and Tamerlan Tsarnaev.

Police officers looked at the program notes as they arrive to the memorial service.

Thousands of Massachusetts Institute of Technology students, faculty, and staff as well as law enforcement officials from across the nation were expected to attend the service.

Security was tight at MIT, according to Boston Globe reporter Peter Schworm.

Members of a police honor guard, front, led a column of law enforcement officials into the memorial service.

On April 23, Officer Sean Collier was made an honorary member of the MIT alumni association.

A photograph of Officer Sean Collier was attached to a cross at a makeshift memorial on the MIT campus in Cambridge.

A Massachusetts state trooper saluted during the memorial service.