article_snippet: The two brothers shot dead the campus police officer on April 18, after investigators released pictures of The two brothers as the primary suspects in the bombing.
article_snippet: An MIT graduate student who was riding his bike by the scene of the shooting identified Dzhokhar as the man An MIT graduate student who was riding his bike by the scene of the shooting saw leaning into slain MIT police officer Sean Collier's police cruiser the night An MIT graduate student who was riding his bike by the scene of the shooting was killed.
article_snippet: slain MIT police officer Sean Collier was shot six times, including three times in the head at close range.
article_snippet: On cross-examination, the defense pointed out that none of the blood tested on Dzhokhar's sweatshirt matched Officer slain MIT police officer Sean Collier .
article_snippet: A MIT graduate student has identified Dzhokhar as the man A MIT graduate student saw leaning into Dzhokhar's sweatshirt matched Officer Collier's car on the night of the shootout .
article_snippet: Dzhokhar was a student at University of Massachusetts Dartmouth when the bombings happened.
article_snippet: Dzhokhar brother briefly attended Bunker Hill Community College .
highlights_snippet: However, none of slain MIT officer Sean Collier's blood was found on Dzhokhar Tsarnaev's .