Way of the Lawless by Max Brand

By one thing he knew the utter desperation of Hal Dozier. For the man had fired while Andrew's back was turned. The bullet had followed the warning cry as swiftly as the strike of a snake follows its rattle. Luck and his sudden leap forward had unbalanced the nice aim of Dozier, and perhaps his mental agitation had contributed to it. But, at any rate, Andrew was troubled as he cleared the edge of the trees and cantered Sally not too swiftly along the Little Silver River toward Las Casas mountains, a little east of south.

He did not hurry her, partly because he wished to stay close and make sure of the number and force of his pursuers, and partly because he already had a lead sufficient to keep out of any but chance rifle shots.