A.T. Robertson Commentary Mark 12:5

"And he sent another; and him they killed: and many others; beating some, and killing some." — Mark 12:5 (ASV)

Beating some and killing some (ους μεν δεροντεσ, ους δε αποκτεννυντες). This distributive use of the demonstrative appears also in Mt 21:35 in the singular (ον μεν, ον δε, ον δε). Originally δερω in Homer meant to skin, flay, then to smite, to beat. Αποκτεννυντες is a μ form of the verb (αποκτεννυμ) and means to kill off.