Vivid Account of Brothers vs. Police

Joby Warrick at the Wash Post has a full account of the Thursday night/Friday morning showdown between the Boston bomb suspect brothers and police with new details.  But it's still unclear why they shot that MIT cop.  It guaranteed they'd get caught or killed and there was no reason to approach the poor guy in his car.  Only motive so far: they wanted to spark battle with police, go out in blaze of glory or something.  If true, then, you'd think younger bro would have later killed himself, when he had so many opportunities to do so.  Perhaps he really a puppet of older bro and when he was gone things changed.

Also, this account suggests that maybe younger bro really did kill older bro when he ran over him with his car:

Tamerlan Tsarnaev, now out of his car, attempted to lob a makeshift bomb at police, but the device exploded in his hand. While Tsarnaez was firing a pistol with the other hand, police tackled and tried to subdue the 200-pound amateur boxer.

Dzhokhar Tsarnaev, apparently intending to help his brother, tried to ram the officers with the Mercedes. Instead, the officers lunged out of the vehicle’s path and he ran over his brother and dragged him along the street before speeding off with police in pursuit.