What is 'man' here?
The colonel and his fellows invade Mayor Orden's village and they are going to shoot a man who does not obey them in the square.
Lanser: Colonel Lanser
Loft: Captain Loft.
Orden: Mayor Orden
Captain Loft gathered his papers and Lanser asked, "In the square, Captain?"
"Yes, in the square. It must be public," Loft said.
And Orden said, "I hope you know."
"Man," said the colonel, "whether we know or not, it is what must be done."
Is 'man' here an interjection like wow or it refers to a person?