A lot of speculation here

The running soldier may be breaking cover as shown below

The general demeanor of the soldier behind the tankdestroyer are showing little concern especially if the tank is about to engage a target which seems unlikely as it appears to be unmanned

The photographer is behind cover or is not in the line of fire but in poor position if the tank were preparing to engage with its main gun - "76 mm gun on the M4 Sherman was found to have an undesirably large muzzle blast that kicked up dust from the ground and obscured vision for further firing." The m36 Jackson was equipped with a 90 mm main gun making the a potential muzzle blast greater. Again unlikely that the Jackson is about to engage.

The medic appears to be responding to a threat - but a random shot could provoke this responce