Parting Shot — 4.22.13

Massachusetts Institute of Technology student Hajar Boughoula of Bizerte, Tunisia, writes a message on the ground with chalk near a makeshift memorial for fallen MIT police officer Sean Collier on the school’s campus in Cambridge, Mass., Monday. Collier was fatally shot on the MIT campus Thursday. Authorities allege that Boston Marathon bombing suspects Tamerlan and Dzhokhar Tsarnaev were responsible. (AP Photo/Steven Senne)