Warning: video is pretty brutal to watch
The "toy gun" wasn't the pink plastic water pistol you imply. It shot BBs and was modified to look real.
"Open carry" doesn't mean you can point a realistic gun at people, especially cops, and expect anything less than a promptly delivered Darwin Award.
The parents are at fault for doing a terrible job of supervising their son. Now the poor cop has to live with the awful consequences of their failure to raise a properly monitored and disciplined child.