How many US presidents have directly killed someone?

I have often wondered this… it’s pretty obvious that George Washington and Andrew Jackson have killed people, but what about FDR or Gerald Ford or Franklin Pierce?

I suspect that most of the presidents up until the early half of the 20th century have directly killed someone at one point, especially the presidents who were alive for the Revolution or the War of 1812 or Indian Wars, since killing would have just been a part of life during those times.

What do you think, Fluther? How many presidents have directly and personally killed someone else before?

(note that I am not talking “killed” in the “Bush lied, people died” way or whatever the conspiracy du jour is. I mean directly killed with a sword, a gun, bare hands, etc.)