Prosecutors say Dzhokhar Tsarnaev or his brother killed CCTV officer Sean Collier , 27 , days after the bombing in a failed attempt to steal his gun . Jurors were shown MIT footage of two suspects fleeing the scene . A photo of Collier 's bloodied gun and holster was also presented in court . Sergeant Clarence Henniger testified to finding Collier shot and gurgling blood in his cruiser on April 18 in 2013 . Grad student Nathan Harman , 24 , said that he saw Dzhokhar near the scene . In the fifth day of testimony , the jury was also shown remnants of the homemade bomb and a piece of a tattered black and white backpack .
Prosecutors say Dzhokhar Tsarnaev or his brother killed MIT officer Sean Collier , 27 , days after the bombing in a failed attempt to steal his gun . Jurors were shown CCTV footage of two suspects fleeing the scene . A photo of Collier 's bloodied gun and holster was also presented in court . Sergeant Clarence Henniger testified to finding Collier shot and gurgling blood in his cruiser on April 18 in 2013 . Grad student Nathan Harman , 24 , said that he saw Dzhokhar near the scene . In the fifth day of testimony , the jury was also shown remnants of the homemade bomb and a piece of a tattered black and white backpack .