A new report recounts in chilling detail how the Boston bombing suspects were hoping to add to their arsenal when they allegedly murdered young police officer Sean A. Collier with five gunshots.
Collier, 27, was about to start a new job with the Somerville Police Department when he was killed.
Friends and family described him as born to be a police officer.
Police believe the Boston bombing suspects shot Sean Collier five times before attempting to steal his gun
The Boston Red Sox line up during a tribute to victims of the Boston Marathon bombing and its aftermath, as an image of Collier is displayed on the scoreboard
'He came to see me a couple of months ago and he said, ‘Chief, I have a chance to get on the Somerville Police,'' MIT Police Chief John DiFava told the Boston Globe. 'I said, ‘Sean, you owe me nothing. You’ve done a fine job for me. I would never stand in the way of someone trying to do better for themselves.’'
On the night Collier died, he was on duty near Kendall Square in Cambridge.
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DiFava had ordered extra campus security in the wake of the bombings. Collier joined the MIT force in early 2012 and was reaching the end of a 3 to 11:15 p.m. shift.
By 9:30 p.m. he was on routine patrol, parked in the corner of Vassar and Main streets.
Collier, who's lifelong dream was to be a cop, was set to join the Somerville Policed Department
Police still have questions about why the suspects were at MIT and what attracted them to attack Collier
The spot gave him a vantage point to see where drivers might commonly make an illegal shortcut through campus to avoid a red light.
DiFava said he'd pulled his car next to Collier's to see how he was doing.
'Just making sure everybody behaves,' Collier replied.
The two men talked for a few minutes before DiFava pulled away.
Half an hour after the DiFava got home, the deputy chief called him.
Robert Rogers, left, puts his hand on his stepbrother, Andrew Collier, after delivering the eulogy at a memorial service for Collier
Collier was appointed to the Somerville Police Department posthumously to honor his sacrifice
'He said Sean Collier has been shot,' the DiFava remembered.
'From the time I saw him to the time he was dead, it was probably about an hour.'
Since then, law enforcement has called what happened to Collier an assassination.
Surveillance camera video shows the two suspects creeping up on Collier's squad car from behind.
He was shot five time, police said. Two of those rounds were to the head.
'He didn't stand a chance,' DiFava said.
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Honor guard: Massachusetts Institute of Technology police officers march as they depart St Patrick's Church in Stoneham, Mass., following a funeral Mass for Collier
Guard of honor: Police officers line up outside St Patrick's Church in Stoneham prior to the funeral for Massachusetts Institute of Technology (MIT) Police Officer Sean Collier
Friends, family and law enforcement officials gather outside the Church for the funeral of Officer Sean Collier who was shot dead by the Boston Marathon bombing suspects
Grief: A mourner walks out of St Patrick's Church following Sean Collier's funeral in Stoneham, Massachusetts
Mourners arrive at the funeral for MIT officer Sean Collier
The suspects allegedly tried to take Collier's gun but were unable to unlock it.
'The retention holster does its job well, so perhaps they didn’t get the gun because of that holster,’' DiFava said. 'Maybe that’s what thwarted them from getting the gun, because the gun was not removed from the holster.'
It's still uncertain why the Tsarnaevs were at MIT or what attracted them to Collier.
Boston's Finest: Police officers march past St Patrick's Church following the funeral service of Sean Collier on Tuesday
B Strong: A woman wearing a Boston Marathon runner's jacket watches as police officers file into St Patrick's Church for the funeral of MIT police officer Sean Collier
'We have all kinds of unanswered questions,' DiFava said.
Last week, the city's Board of Alderman posthumously appointed Collier to the police force.
Collier was laid to rest on Tuesday at a private funeral Mass for Officer Collier held at St Patrick's Church in Stoneham, Massachusetts.
Heartbroken: Mourners leave the private service on Tuesday for Officer Collier
Shock: There were emotional scenes as mourners lined the streets outside St Patrick's Church as Sean Collier's coffin was removed
Comfort: Priests offer words to mourners on leaving the Church in Stoneham, a small town close to Boston
'Our only solace is that Sean died bravely doing what he committed his life to - serving and protecting others,' his family said in a statement.
He was a Wilmington native and a graduate of Salem State University. He is survived by his parents and five siblings.
The young officer enjoyed climbing mountains, training young boxers and playing kickball on a team called Kickhopopotamus - but most of all, he was dedicated to being a police officer.
Support: Young men embrace following the 27-year-old's funeral after he was killed in the line of duty
Remembrance: A tribute honoring fallen Massachusetts Institute of Technology police officer Sean Collier is seen on a window of a truck
Officer Collier impressed students and his colleagues with his contagious enthusiasm, be it offering students rides or volunteering for extra duties.
DiFava said on days before the service: 'Just the other day - and I still have it on my computer - he asked me if I would have a problem if he approached the homeless shelter to see if he could become a member of the board of directors, so that he could work with those people down there and try to mitigate problems before the problems develop.