Departamento de Policía del Instituto Tecnológico de Massachusetts

El 18 de abril de 2013, alrededor de las 22:25, el agente de patrulla del MIT, Sean Collier, de 27 años, ^{[ 6 ]} de Somerville, Massachusetts , fue baleado en su patrulla mientras estaba sentado afuera del Centro Stata del MIT . Collier fue trasladado al Hospital General de Massachusetts, donde fue declarado muerto. ^{[ 7 ] [ 8 ] [ 9 ]} El Instituto aconsejó a los miembros de la comunidad del MIT que se encontraban en el campus o cerca de él que permanecieran en el interior. ^{[ 10 ]} Un sospechoso fue abatido a tiros posteriormente; el otro fue capturado al día siguiente. ^{[ 11 ] [ 12 ] [ 13 ]} La investigación policial sugirió que los sospechosos dispararon a Collier para armarse aún más. Algunos funcionarios encargados de hacer cumplir la ley dijeron que los sospechosos buscaban provocar un enfrentamiento a gran escala con la policía. ^{[ 14 ]} Collier había sido miembro del Departamento de Policía Auxiliar de Somerville de 2006 a 2009. ^{[ 15 ]}

One week after the shooting, Collier's open-air memorial service was attended by more than 10,000 people—including thousands of police officers from the New England region and Canada—in a ceremony hosted by the MIT community.^[6][16][17] On November 25, 2013, MIT announced the creation of the Collier Medal, to be awarded annually to "an individual or group that embodies the character and qualities that Officer Collier exhibited as a member of the MIT community and in all aspects of his life". The announcement added that "Future recipients of the award will include those whose contributions exceed the boundaries of their profession, those who have contributed to building bridges across the community, and those who consistently and selflessly perform acts of kindness".^[18][19][20]

There was a spontaneous, improvised temporary memorial to Collier on the MIT campus; the design for a permanent one at the same site was unveiled at an April 2014 ceremony commemorating the one-year anniversary of the bombings and his murder. At that occasion, Cambridge Mayor David Maher announced that the corner of Vassar Street and Main Street, near where his shooting took place, would be renamed "Officer Sean Collier Square". Representatives from his family and MIT ran in the 2014 Boston Marathon to raise money for a scholarship in his honor. His name has been inscribed in the Cambridge Police Department's memorial to its fallen officers.^[21] The permanent memorial is a granite structure resembling an open hand of peace inviting contemplation, designed by MIT Architecture Associate Professor J. Meejin Yoon. The memorial was completed, and a dedication ceremony was held on April 29, 2015.^[22]