Seeing an unknown young black man who forcibly enters your home without invitation after ringing the doorbell is a dammed good reason to be in fear of losing life or experiencing great bodily harm.
In fact, the man does not need to be black or young. Race is the most minor factor in a probable response. The pattern is "home invasion". The assessment and response choices must be made in about one fifth second if the door is already open.
The most probable correct response is to shoot the intruder immediately. That is particularly so if you are older and not able to physically resist the person in front of you. There are no second chances if you guess wrong.
Notice how the story keeps changing with additional details being disclosed.
Was the door opened before shots were fired or afterwards?
Who opened the door?
Did the young man enter the home?
Did the young man say anything to the homeowner?
Did the young man touch the homeowner?
I expect the young man was convinced that his siblings were in that house and was righteously aggressive, belligerent, and demanding that the homeowner produce them. Not smart tactics when approaching an unfamiliar residence.
The boy didn’t enter the home. He was shot through the glass outer door. According to Lester himself, they did not exchange words.
Face it. The kid did not enter the house nor did he demand anything. The old man shot him through the glass because he was scared and then he opened the door and shot the kid in the arm while he was on the ground.