Could be spinal/brain damage or a direct shot to the heart. Either of those would drop someone instantly. However without access to an autopsy report we won’t know.

The stiffening happens with a good portion of shooting victims. Getting shot is a lot of kinetic energy being put into a body and that causes all sorts of bodily systems to misfire.

Don’t get me wrong, I’m not saying these fucks could have saved him just that you have longer than 30 seconds to live with most gunshot wounds. Especially if you’re given life saving aid rapidly.