A TTAG commentator writes:
According to boston.cbslocal.com, Dzhokhar and Tamerlan Tsarnaev walked up to the MIT officer’s car and shot him in the head, unprovoked. It appears to be an assassination. But why? How did that fit into their plan? The operating theory: they were short one gun. The older brother had a gun. They wanted to get a gun for the younger brother. The fastest and most efficient way they could think of doing it was a surprise attack on a cop, to take his weapon and go. Officer Collier had a retention holster; it’s like a three-way lock. If you don’t know how to remove the gun, you’re not going to get it out. There was apparently an attempt to yank it. The Tsarnaevs couldn’t get it and left. Regardless, this is exactly what will keep happening if any sort of real clamp-down occurs on buying guns: bad guys will simply kill to acquire them.