What really happens when a Promethean is killed?

When you kill a Promethean and they disintegrate into the orange sparks, what actually occurs? Does the Promethean truly die or does its “soul” just return to some kind of data bank? Also another question I have concerns crawlers and watchers. Are they also composed ancient humans or simply machines meant to help the Promethean?

I guess we could say that their “soul” dissappears after the few moments it remains. ANd I think that Crawlers and Watchers are just machines to assist the Prometheans.