No that's not fake. This ad actually ran in newspapers. Making things even worse: It was 1939, when the United States was still in the thrall of the Great Depression. It was a tough, desperate time, and families everywhere were slowly starving to death while facing grim choices and hard realities.
Every picture tells a story, and this one only gets worse the more you think about it. You might assume we've stumbled upon Dad's suicide note while he's off working up the nerve to make it a memorable Christmas. But notice that the note is written in the second person. That can only mean that this note is written to dad, essentially saying: "Look, we're not going to kill you. But if your failure to provide for this family makes you want to kill yourself, well, Merry Christmas. It's a Colt, so even you should be able to do this job.