{Of the evil one} (ek tou pon(8872)ou). Ablative case and the
same for neuter and masculine singular, but verse  10  makes it
clear that the reference is to the devil. {Slew} (esphaxen).
First aorist active indicative of sphaz(935c), old verb, to slay, to
butcher, to cut the throat (Latin _jugulare_) like an ox in the
shambles, in N.T. only here and Rev. ( Re 5:6,9,12 , etc.).
{Wherefore?} (charin tinos;). "For the sake of what?"
Post-positive preposition ( Eph 3:1,14 ) except here. The
interpretation of the act of Cain ( Ge 4:8ff. ) is an addition to
the narrative, but in accord with  Heb 11:4 . Jealousy led to
murder.