The grad rockets landed within 10-20m of each other meaning that the distance of the launcher was about 500m-1km away and fired at short distance also their is no sign of Grad Rockets hitting the ground near the bus.
The grad strikes are rounded whereas the explosion near the bus is square in patern meaning it wa a controled device and not grad strike. You can also see with the Grad strikes the dispersal pattern which shows the direct in which they were fired, the darker spots indicate where therocket hit and the lighter shades indicate the direction in which the grad strikes were heading.
Dashcam Video of Explosion that Struck Bus
Hence the the grad laucncher must have been behind the first camera angle and fired over the top of the check point indicating they came from Ukraine held territory.
Also the bus is parked off to the side so its looks like a military transport its not waiting to pass at the checkpoint either, the people at teh checkpoint also seem to be walking around casually considering their is a Grad Strike in progress thay arent even trying to take shelter.