dexter streets to face what amounted to chaos. >> they have explosives, some type of grenades, they're in between houses down here. >> loud explosions! loud explosions! shots fired! >> reporter: the tsarnaev brothers were in the middle of the streets firing home-made bombs, in return, facing a massive barrage of police bullets. two local law enforcement source tell cnn, the tsarnaev's had one gun between them. when the older brother, tamerlan, was tackled by police, that one gun was empty. it was the moment his younger brother tried to make a run for it in a stolen suv. >> there was a lot of gunfire at that point. that was probably the highest point in gunfire and really as soon as the suv turned around in the street, it was justing a