St Ezekiel lived about 593 years before Christ. The Hebrew letter Tav/Taw at that time was written as a cross.
All protestant translations that came after the Taverner’s Bible (1551) stopped having the cross mentioned and started calling it a ‘mark’. The Catholic translations to this day still say the name of the Hebrew letter, cross, or X.
Ezechiel 9:3-6 (Douay Rheims)
And the glory of the Lord of Israel went up from the cherub, upon which he was, to the threshold of the house: and he called to the man that was clothed with linen, and had a writer’s inkhorn at his loins. And the Lord said to him: Go through the midst of the city, through the midst of Jerusalem: and mark Thau upon the foreheads of the men that sigh, and mourn for all the abominations that are committed in the midst thereof. And to the others he said in my hearing: Go ye after him through the city, and strike: let not your eyes spare, nor be ye moved with pity. Utterly destroy old and young, maidens, children and women: but upon whomsoever you shall see Thau, kill him not, and begin ye at my sanctuary. So they began at the ancient men who were before the house.
Ezechiel 9:3-6 Knox’s Bible (1945)
and now, borne on cherub wings, the glory of Israel’s God rose above the threshold of the house, summoning him of the linen clothes and the ink-horn to set about his task. Make your way, the Lord said to him, all through the city, from end to end of Jerusalem; and where you find men that weep and wail over the foul deeds done in it, mark their brows with a cross. To the others I heard him say, Yours it is to traverse the city at his heels, and smite. Never let eye of yours melt with pity; old and young, man and maid, mother and child, all alike destroy till none is left, save only where you see the cross marked on them. And begin first with the temple itself.
Ezekiel 9:3-6 (New Jerusalem Bible)
The glory of the God of Israel rose from above the winged creature where it had been, towards the threshold of the Temple. He called to the man dressed in linen with a scribe’s ink-horn in his belt and Yahweh said to him, ‘Go all through the city, all through Jerusalem, and mark a cross on the foreheads of all who grieve and lament over all the loathsome practices in it.’ I heard him say to the others, ‘Follow him through the city and strike. Not one glance of pity; show no mercy; old men, young men, girls, children, women, kill and exterminate them all. But do not touch anyone with a cross on his forehead. Begin at my sanctuary.’ So they began with the old men who were in the Temple.
Ezekiel 9:3-6 (New American Bible)
Then the glory of the God of Israel moved off the cherub and went up to the threshold of the temple. He called to the man dressed in linen with the scribe’s case at his waist, and the LORD said to him: Pass through the city, through the midst of Jerusalem, and mark an X on the foreheads of those who grieve and lament over all the abominations practiced within it. To the others he said in my hearing: Pass through the city after him and strike! Do not let your eyes spare; do not take pity. Old and young, male and female, women and children—wipe them out! But do not touch anyone marked with the X. Begin at my sanctuary. So they began with the elders who were in front of the temple.