John Gill Commentary 2 Samuel 20:12

"And Amasa lay wallowing in his blood in the midst of the highway. And when the man saw that all the people stood still, he carried Amasa out of the highway into the field, and cast a garment over him, when he saw that every one that came by him stood still." — 2 Samuel 20:12 (ASV)

And Amasa wallowed in blood in the midst of the highway
By which it seems, that though the wound was mortal, and of which he died, that as yet there was life in him, and through the pain he was in, and the pangs of death on him, he rolled himself about in his own blood in the high road, where the fact was committed:

and when the man saw that all the people stood still ;
gazing at the shocking sight, and could not be prevailed upon to go on:

he removed Amasa out of the highway into the field ;
which was adjoining to it:

and cast a cloth upon him ;
that the body might not be seen:

when he saw that everyone that came by him stood still ;
and so retarded the people in their march, to prevent which he took the above method, and it was a very prudent one.