What decision does George make about Lenny when he Says, "I aint gonna let 'email hurt lennie"

George has already made the decision to kill Lennie before the rest of the man get a hold of him. 

"He said sharply, “I ain’t gonna let ‘em hurt Lennie. Now you listen. The guys might think I was in on it. I’m gonna go in the bunk house. Then in a minute you come out and tell the guys about her, and I’ll come along and make like I never seen her. Will you do that? So the guys won’t think I was in on it?”