There are two stories, Lester (the old man) said Ya was pulling on the door, Yarl says he didn’t. Investigators said that Lester shot through the storm door.
The story from nbc said that Lester shot once, yarl fell to the ground and Lester shot again.
Again, all that doesn’t matter, pulling on a storm door (if he actually did that) is not “breaking in”, it could be that Yarl was just trying to get at the main door to knock. In any case, what he should have done is kept the door shut, locked and called the police, and waited…