Well, I can think of a few things. Ditch the snipers rifle for SMGs and sneak into the basement. At 150/160 feet, at nearly two hundred feet looking down scope you don't need a stealth suit. Since you have a way to become invisible sneak into the basement and try to save Caro. 

Were gonna find away to kill him one way or another but it might be a great away to gather everyone together.