Info straight from gearbox

Borderlands 2 features dualwield. And a separate class for each gun type such as pistols,smg's,shotguns,etc. 10 times as much guns then in borderlands. And all the characters from the first borderlands, and the npc's are more active like in elder scrolls IV oblivion they react and can be killed. Not to influence you to go around killing everyone seeing as though it will stop the story and not allow you to move on in the story. So put thought into how you interact with npc's. Remember they will have new guns and you do not continue from borderlands. Borderlands 2 will be great and be sure to buy it. Remember this is straight from the source of the head gun producers son.