What is the nature Lennie's attack on Curley's wife?

Curley's wife is terribly lonely. She seeks companionship with the only person who will talk to her. She finds Lennie with his dead puppy in the barn. Lennie has smothered his puppy to death. Curley's wife allows Lennie to stroke her hair and things go downhill from there. Curley's wife panics and Lennie, thinking he will get in trouble from George, inadvertently kills her. 

I mint to say : what is the nature of his attack 

Lennie didnt kill Curley’s wife intentionally. He was petting her hair but she started screaming, he got panicked and couldn’t think of anything. Her neck was broken accidentally and she died. The true nature of his attack was that he didnt want her to scream and get him in trouble. He was trying to save himself that George dont get mad.