“Everything Zechariah said was a foretelling of the future. Led by the prophetic spirit to the knowledge of hidden mysteries, and aware of the mystery of virginity that surrounds the incorrupt birth, he does not remove the Virgin Mother from the place in the Temple that the law reserves to virgins. He explains to the Jews how the Creator and King of all creation holds human nature subject to himself, together with all other things, so that he governs it according to his pleasure and is not controlled by it.
Thus it is within his power to create a new kind of generation, which does not prevent a mother from remaining a virgin. This is the reason why Zechariah does not remove Mary from the place in the Temple reserved to virgins. The place in question was an area located between the temple [court] and the altar.* The Jews, having heard that the King of creation, according to his divine pleasure, had come through a new kind of birth, and fearing to be subject to a king, slew Zechariah while he, in his capacity as priest, was offering the sacrifice in front of the altar, because he had witnessed to the events relating to [Christ’s] birth.”
*[According to this tradition, the father of John the Baptist is to be identified with Zechariah, son of Barachiah, of whom Jesus speaks (cf. Mt 23:35).]Gregory of Nyssa , On the Birth of Christ, PG 46, 1137 A-B.
This was a tradition common to St. Gregory’s time. Origen and Basil mentioned it in their writings. Whether this story truly happened or not, I think everyone who tries to do good is persecuted by the powers of this world. It is our job to do God’s work. If we choose to do His work and His commandments, we remain alive, even if we were physically killed.
Gambero, L., 1999. Mary and the Fathers of the Church 1st ed. Translated by Buffer, T., San Francisco: Ignatius Press. p. 156.