Nothing is known about this man before the outbreak began, except that he worked for the Border Patrol agency.
While Colton was in the Construction Site, standing guard over the entrance to The Tunnel, this man and the Unnamed Border Patrol Guard were in the tunnel itself, presumably clearing it of Infected. When Sierra tripped the booby trap, this border patrol guard began searching the tunnel.
This guard is searching the tunnel for Sierra when a mining cart roles up behind the Unnamed Border Patrol Guard. He is slow to react when and Infected is shoved into his colleague by Sierra. The last we see of him is being hit on the head by Sierra.