Why bury a bow and arrow in front of the grave? I haven't heard of it anyway. The objects and shapes around the yin house are taboo, and future generations are prone to criminal injuries and disasters. When burying bows and arrows, future generations are easy to argue, fight, go to jail, kill or be killed, and criminals are easy to be assassinated. It's easy to get a gun, but it's hard to guard against an arrow in the back.
If you want to do evil in front of someone else's ancestral grave, you'd better not. If you hurt the virtue, you will get what you deserve.