Context is the Key
In order to establish a proper understanding of Ezek. 9, we must establish the context of the verses, which is established in Ezek. 8:3,
And he put forth the form of an hand, and took me by a lock of mine
head; and the spirit lifted me up between the earth and the heaven,
and brought me in the visions of God to Jerusalem, to the door of the
inner gate that looketh toward the north; where was the seat of the
image of jealousy, which provoketh to jealousy.
Since the "Chapters" were separated much later in time, we must read from Ezek. 8-9 without any interruption, which is normally the case when an author 'assigns' a chapter to a particular train of thought. Ezekiel is "caught up in the spirit", meaning he is seeing what God is seeing in the realm of the spirit world, so angels, spirit beings, God or manifestations of God are readily seen, and concrete, opaque structures(such as the Temple) are seen right through, just as God sees through everything physical and temporal.
Keil and Delitzsch offer this commentary in regard to the 'men' of Ezek. 9:1,
Consequently פּקדּות are those whom God has appointed to watch over the
city, the city-guard (2 Kings 11:18), - not earthly, but heavenly
watchmen, - who are now to inflict punishment upon the ungodly, as the
authorities appointed by God.
Furthermore, they add,
In the midst of the six men furnished with smashing-tools there was
one clothed in white byssus, with writing materials at his side. The
dress and equipment, as well as the instructions which he afterwards
receives and executes, show him to be the prince or leader of the
others. Kliefoth calls in question the opinion that these seven men
are angels; but without any reason. Angels appearing in human form are
frequently called אנשׁים or אישׁ, according to their external habitus
The "Watchmen" are those angels assigned territorially by God, to protect or to execute His Judgements. What is interesting in this passage is that those who "escape these judgements" are those who "sigh and cry for all the abominations done in them", and what is more, is they are "marked"; some versions say "with a 'tau'".
This is very significant, as God had Israel "mark" their doorposts and lintels in Egypt to escape destruction, and we see this passage as a precursor to the "mark" or "sign" that God gives to His servants,(Rev. 7:3)
"Saying, Hurt not the earth, neither the sea, nor the trees, till we
have sealed the servants of our God in their foreheads."
We can therefore conclude a "biblical pattern" of God "marking" or identifying out those who will escape judgement from the rest who do, and it is the "watchmen" or angels who are assigned to carry out those judgements.