The Vertex by Kevin_D

When a Marine reconnaissance unit investigates the deaths of the Al Qaeda leadership, they unwittingly place themselves along the path of a technological supersoldier. Worse, their actions have exposed a covert US black-op whose sole purpose is to exterminate all witnesses: including other Americans.

Marine vs terrorist. American vs American. Human vs machine. The ultimate attritional free-for-all has begun, with no rules, no mercy, and an entire country caught in the crossfire. Outmanned, outgunned, and with nowhere to hide, the Marines must make a choice between saving themselves and saving the entire human race...