Clearly, the first charge that could be issued against these two men would be a charge of robbery. The two clearly took money from the old woman through the use of force. That charge is essentially indisputable.
A charge of murder could be brought, though that one would be harder to prove. The basic issue would be whether the men could reasonably have foreseen that their actions (which were clearly illegal) would lead to the death of the woman. A prosecutor could clearly make a case that the men should have known this. It is reasonable to assume that knocking an old woman (depending on how old and frail she looked) to the pavement could well lead to her death. However, the defense would surely argue that the men could not have intended or foreseen her death and could not, therefore, be guilty of murder.