Why did he answer the door?
Even if he thought some bad guy was on the other side, he was at a disadvantage opening that door. Gives the other guys on the side a clear shot to kill him and he's out of position.
Why not wait inside the home, from an advantageous position, and kill the intruder by catching him by surprise once he enters the home?
If you wait inside, you at least give yourself a fighting chance, be they cops or robbers. You're closer to your ammo, you can be closer to protecting your family, closer to a phone if you need it...it just makes sense.
My weapon is under the bed. You have to come into my house if you want to see it. But you'll only see it once.
seriously? how old are you? you actually believe the cops knocked on that guys door and he opened it? they hamered the door a few times, heard noise inside,.. one wanabe top cop heard a gun get cocked... he figured, ''this is my moment'' he kicks in the door scared as shit, to see some dude holding a gun,,[also, scared as shit] but the cop is trained to kill,lol, and fires the shot. thats the story.