There are really two sets of events in “Contents of the Dead Man’s Pocket” that explain why Tom Benecke went out on the ledge. One set of events happens in the time the story is being told. The other set of events has already happened by the time that the story begins.
The events that happen just before Tom goes out on the ledge have to do with the fact that he feels bad about staying home and working instead of going to the movies with his wife. First, he feels hot, which he attributes to his guilty conscience. This causes him to go over and make the effort to open the window. Next, Clare leaves. Tom, conflicted, watches her walk down the hallway for a while instead of closing the door immediately. As he holds the door open, air rushes because of the open window. He now has to push to get the door closed. As this happens, he hears the paper that holds his notes rustling as it is blown off the desk and out the window. He considers what to do for a while, and then goes out the window onto the ledge to get the paper. These are the events that led directly to Tom going out on the ledge.
We can also say that the events that truly sent Tom out on to the ledge happened before the story began. These events have to do with his ambition to rise in his company. Tom decided he wanted to make a name for himself and get himself noticed by the higher-ups in the firm. Therefore, he spent hours doing research on “his idea for a new grocery-store display method.” He wrote up all his findings in shorthand on this one yellow piece of paper. This is why Tom goes out on the ledge. He goes out because his ambition has caused him to spend countless hours on research that will help his career. When the notes from his research go out the window on to the ledge, so does he.