People link hands to form a human chain from a makeshift memorial for fallen MIT police officer Sean Collier to a campus police station at the Massachusetts Institute of Technology in Cambridge, ... more 
People link hands to form a human chain from a makeshift memorial for fallen MIT police officer Sean Collier to a campus police station at the Massachusetts Institute of Technology in Cambridge, Mass., Monday, April 22, 2013. A moment of silence for victims of the marathon bombings was also observed during the event. Collier was fatally shot on the MIT campus Thursday, April 18, 2013. Authorities allege that Boston Marathon bombing suspects Tamerlan and Dzhokhar Tsarnaev were responsible. (AP Photo/Steven Senne) less 
1 / 30
Associated Press | Photo By Steven Senne
Mon, Apr 22, 2013 4:32 PM EDT