Maybe Cain went into the field and "accidentally" tripped Abel so that he fell into the spinning swords guarding the tree of life.
Murder in the Bible.
For a strict bible literalist, there would of course be the logical problem of where the third and fourth humans ever to live on earth would have gotten a sword in the first place.
I.E. - who mined the mieral ore, discovered metallurgy, crafted the sword, etc...at a time when a population of less than half a dozen people would have to have been hunter-gatherers to have a minimal survival.
Unless, of course, the fundamentalist waves his hands in the air and proclaims that God gave them the sword.
cain, killed mr mint sauce, in the field, with.......