>> police are in a fight for their lives. >> at that point one of the shooters actually started charging the officers, running down the street still firing his weapon. >> and they're literally about ten feet away from each other exchanging gunfire. and then he runs out of ammunition, the bad guy. >> the bad guy, tamerlan, throws his empty gun at officers who then tackle him to the ground. >> when dzhokhar saw what was going on with his brother, he jumps into the mercedes suv and comes back at the cops who are on top of his brother. >> dzhokhar aims the car straight at the officers. >> somebody at the last minute yelled get out of the way and they drove out of the way. >> instead, he runs over his brother. >> fatal injuries on tamerlan tsarnaev were inflicted by his brother dzhokhar who ran him over. >> dzhokhar tsarnaev makes his escape. he is wounded and bleeding and looking for a place to hide.