Lennie begged, "Le's do it now. Le's get that place now." "Sure, right now. I gotta. We gotta." And George raised the gun and steadied it, and he brought the muzzle of it close to the back of Lennie's head. The hand shook violently, but his face set and his hand steadied. He pulled the trigger. The crash of the shot rolled up the hills and rolled down again. Lennie jarred, and then settled slowly forward to the sand, and he lay without quivering.

Lennie begged, “Le’s do it now. Le’s get that place now.”
“Sure, right now. I gotta. We gotta.”
And George raised the gun and steadied it, and he brought the muzzle of it close to the back of Lennie’s head. The hand shook violently, but his face set and his hand steadied. He pulled the trigger. The crash of the shot rolled up the hills and rolled down again. Lennie jarred, and then settled slowly forward to the sand, and he lay without quivering.

– John Steinbeck

Of Mice and Men, Chapter 6. George shoots his best friend Lennie in the back of the head, to save him from prison or a worse fate at the hands of Curley.

John Steinbeck Quotes