Vice President Joe Biden attended the service for Collier, an officer at the Massachusetts Institute of Technology, along with students, staff and faculty from the university and hundreds of police officers, the Boston Globe reported. Collier, 27, was gunned down Thursday night in his squad car.
Rob Rogers, Collier's brother, said Collier was "born to be a police officer."
"If there is anything that we can learn from this, it is the morals and beliefs that Sean exemplified during his time in service. Respect. Support. And caring,'' Rogers said. "He has taught me that a smile to a stranger, a simple hello, an outreached hand can ultimately change how people treat each other.''
Collier's coffin was carried into Briggs Field by an honor guard of MIT officers. Security was tight with the crowd of more than 10,000 having to pass through checkpoints and show ID.
"Officer Collier did not just have a job at MIT, he had a life at MIT," MIT President Rafael Reif said.
Maddie Hickman, an MIT graduate, echoed that statement.
"He was a really good friend, a really funny guy,'' Hickman told the Globe before the service began. "Everybody loved him. I wish he were here.''
A private funeral was held Tuesday at St. Patrick's Church in Stoneham.