Hunting close to private property requires being able to drop the deer in it's tracks to avoid the incident like you posted. While a neck shot or a double front shoulder shot will do it the question is can you. Shooting at the buck after it went back on private property in my opinion broke the law regardless if it was hit or not. Once it crossed the line it was no longer his buck. Could he have asked permission to pursue the buck? I would not hunt where I can see other hunters in sight, makes for a dangerous situation.