Counsel was to kill (βουλη εγενετο ινα--αποκτεινωσιν). The soldiers did not relish the idea of the escape of the prisoners. Hence there came this "counsel" (βουλη). Regular Greek idiom for purpose (ινα and aorist active subjunctive of αποκτεινω, to kill). Soldiers were responsible for the lives of prisoners (Acts 12:19).

Swim out (εκκολυμβησας). First aorist active participle of εκκολυμβαω, old verb to swim out and so away.

Escape (διαφυγη). Second aorist (effective) active subjunctive of διαφευγω, to make a clean (δια) escape.