Death is come up, etc. "Death," equivalent to "pestilence" (as Jeremiah 15:2), the most dreaded foe of a besieged population. (For the figure, comp. Joel 2:9.) The children from without. The ideal of Zechariah is that "the streets of the city should be full of boys and girls playing in the streets thereof" (Zechariah 8:5).
But the pitiless reaper, Death, shall cut off even "the playful child from the street" (so we might render more literally). Streets, in the parallel clause, means the "broad places" where men congregate to toll the news.