I am reading Mistborn 1 again (for the 6th time) and decided that rather than just pondering the text and continue reading as usual, I would voice my 'question' which may or may not have been answered previously. Please move or merge as necessary.
That night, Kelsier had Snapped, coming into his powers as a Mistborn. The next night, men had died.
Many Men.
I assume that since Kelsier was a prisoner in the Pits of Hathsin, outside of atium and minute traces in his own body, he would not have access to any allomantic metals. Unless he discussed allomancy at great length with Mare, he would have had to have been a very quick learner to take one day to master the confusing affects of atium. Even with the one second glimpse into the future, to take on 'many men' would have been a tall feat without the use of pewter, iron or steel.
Therefore, I am lead to believe that there may be much more to the story or a very simple answer, both of which Brandon could possibly divulge here or within a short prequel.
You may ask yourself "Where was his question? I didn't see a question mark anywhere in his post." and I would respond "It was in the last sentence."