A steady stream of visitors paid tribute to MIT police officer Sean Collier in front of Building 32 on Saturday April 20. Collier was slain near this location on April 18 in his police cruiser. Ho Yin Au—The Tech May. 9, 2016 Facebook Twitter Reddit Print A steady stream of visitors paid tribute to MIT police officer Sean Collier in front of Building 32 on Saturday April 20. Collier was slain near this location on April 18 in his police cruiser. Ho Yin Au—The Tech