Students at the Massachusetts Institute of Technology knew Sean A. Collier as their affable campus policeman with a warm smile, the guy who made polite conversation with strangers and reached out to the homeless.
But in death, their everyman police officer, who was allegedly gunned down by the Boston Marathon bombing suspects, drew a crowd of more than 15,000 for a 90-minute memorial service on Wednesday that was befitting a head of state.
They came on a glorious spring day, an outpouring of law enforcement unity that attracted police from as far away as the Midwest and Canada, as well as Vice President Joe Biden, Senator Elizabeth Warren, and thousands of MIT students and staff.
“He will live in our family, and hopefully yours, forever,” said Robert Rogers, the victim’s brother, holding back tears as he spoke to the crowd assembled at MIT’s Briggs Field.
“Big smiles, big heart, big service, all love,” Rogers said of his brother, recalling his younger sibling as a country-music lover who blared tunes from his black Ford F-150 and who took up square dancing although he had “two left feet.”
Collier, 27, was attacked Thursday night near Kendall Square in Cambridge in what Boston Police Commissioner Edward F. Davis has called a “vicious assassination.’’
The attack helped spur a massive law enforcement response that led to a gun battle and the death of bombing suspect Tamerlan Tsarnaev in Watertown and then the capture of his brother, Dzhokhar, after a 20-hour manhunt.
Security at Wednesday’s memorial was heavy, with snipers on rooftops and metal detectors at the entrance, as authorities continue to investigate the Marathon bombing and Collier’s slaying. Prosecutors allege that Collier was killed by one of the Tsarnaev brothers while he was sitting in his cruiser near the university’s Stata Center.
In his remarks to the crowd, Biden called the Marathon bombers “two twisted, perverted, cowardly, knock-off jihadis.”
In 1972, Biden’s first wife, Neilia, and their year-old daughter were killed in a car crash; two other children survived. Biden referred to his own family tragedy in consoling the Collier family, telling them that despite their overwhelming grief, there will come a time when a smile will replace tears.
“No child should predecease their parents . . . I know from experience, that sense of dread, the reliving the moment, the last nine days, almost hourly, the moment you learn the fate of your child,” Biden said.
“The moment will come . . . when you know it’s going to be OK, when the first instinct is you get a smile on your lips before you get a tear to your eye. It’s impossible to fathom that that will occur, but I promise you, I guarantee it will.”
James Taylor performed two songs during the service, “The Water is Wide” with the MIT Symphony Orchestra and an a capella version of “Shower the People.”
“People ask me if Sean were here, what would he think? Are you kidding me? He would love this,’’ Rob Rogers said at the memorial. “You’ve got sirens. Flashing lights. Formations. People saluting. Bagpipes. Taps. The American flag. He would have loved it.’’
“He was born to be a police officer and he lived his dreams,” Rogers added.
For students who knew Collier, the gathering was a time to reflect on happier times.
“He was a really good friend; I met him a little over a year ago at the student center on campus,’’ said Maddie Hickman, 24, of Arlington, a 2011 mechanical engineering graduate.
“We were going on a hiking trip and had a bunch of gear and he came up to us and asked what we were doing. He was super friendly and loved cracking jokes. He always asked if we needed help with anything no matter how busy he was.
“It’s been a pretty hard week, but it’s great to hear all the stories about how he impacted people.”
Michele Pratusevich, a computer science senior who is a member of the school’s Outing Club, also knew Collier.
“He really wanted to get to know everyone, he wanted to be part of the community,” she said. “He made a point to ask everyone what they were involved with, in case he wanted to get involved, too. That’s how he got involved with the Outing Club; we told him to get involved. MIT suffered a big loss, because he was really a big part of it.”
Some police traveled a long way, including 23 officers from the Elizabeth Police Department in New Jersey and two officers from Ohio State University’s Department of Public Safety, who drove for 13 hours.
“Obviously it’s a sad day, but we honor our fallen brothers whenever this occurs,” said Tyrone Torner, a deputy chief with the Elizabeth department. “I grieve for his family.”
Mary Polidori, a detective with the University of Vermont’s Police Department, said the outpouring of support for Collier was well-deserved.
“He died so tragically, but I love to see so many of our brothers and sisters come out to celebrate his life,” she said. “He did more than most officers, trying to reach out to the homeless. It’s amazing.”
Joanna Shaul and Cassandra Shaffer, the officers from Ohio, said they decided to attend the service last weekend and were undeterred by the long drive.
“I’ve always said that campus law enforcement is a little bit different, something special, and it sounds like Officer Collier really understood that and took it to the next level,” said Shaul, who has been with the department for two years.
“He’s certainly an inspiration to me, the kind of officer I want to be like.”
The service was closed to the public, held for MIT students and staff and first responders.
Security was tight, even though most attendees were armed law enforcement officials. Police in SWAT gear with automatic rifles patrolled the perimeter, along with K-9 units. Backpacks were prohibited.
When Martha Poehler walked from her Cambridge home to Wednesday’s memorial service, she knew she would not be able to get onto Briggs Field, but she needed to be there, just the same. So she listened to the service, which drew thousands of people, under a tree just beyond the fenced area. It was, she said, “the least I could do.”
“He sounded like an incredible young man,” said Poehler, 66. “I would have loved to know him.”
Dozens of Cambridge and Somerville residents gathered just outside of the service, bound by a shared sense of obligation to honor Collier’s memory. Some stood on benches or steps to get a better view, while others just listened.
“I just wanted to pay my respects,” said Mickey Barry, 64, a technician at Draper Laboratory in Kendall Square whose good friend knew Collier well.
Maurice Martin, a neighbor of Collier’s in Somerville, wasn’t able to get into the service, but watched it on television at a campus building nearby.
“He was a hell of a good guy,” he said. “It meant something for me to be here.”
As the strains of bagpipes hung in the air, Constanza De La Carrera, 23, was touched by the vast display of public grief.
“It’s very emotional,” she said. “It’s beautiful to see.”
Brian Ballou can be reached