Do not ever let a person get that close to you in an armed conflict, and do not pull a gun out to aim at the ground.

Safety off, level stance by or behind cover, aim center of mass and lead the target.

At that range it's a weighted coinflip in favor of the guy on the lawn in rushing down the guy on the porch. When he moves up to the porch it is virtually impossible for the guy with the gun to respond in time if the thief pulls a knife.

Again, everything this guy did was wrong. If the thief was slightly more aggressive he'd be dead.