Who’s right/wrong in crash?

[duff_duffy]

Today I saw biker on sidewalk on wrong side of road ride straight into marked crosswalk at 4 way stop. Car coming perpendicular hit bike rider after going through intersection (pretty much hit biker straight on). Bike jacked up, slight car damage, rider hit head but seemed ok but shook up. Driver kept saying she came out of nowhere. I always thought in a crosswalk it’s drivers fault all the time but when I saw the speed at which this happened wonder legally who’s right. Biker did not stop going into the intersection, I assume car had stopped at far side but did not see that part. In NJ