This is highlighted by National Geographic as showing the high level of violence of that civilization.

The Indus civilization was based in parts of what is now Pakistan and India. and has sometimes been compared favourably to Egypt and Mesopotamia as having, supposedly, lower levels of inter-personal violence. Now a look at the skeletal remains indicates, with some reservations, that that's not so:

Of the 18 skulls examined from this time period, nearly half showed serious injuries from violence, researchers reported in a recent paper in the International Journal of Paleopathology. The rate of skull injuries tied to violence is the highest recorded in the prehistory of South Asia, the researchers say. It may be no coincidence that at the time of these burials the Indus civilization was beginning to disintegrate and parts of Harappa were being abandoned, for reasons that scholars are still debating. ...
New Views of Ancient Culture Suggest Brutal Violence

This is interesting as showing that while people -- even scholars -- in our current society are often willing to fantasize about the supposed peacefulness of any society from the past they know little about, once one looks closer such dreams tend to dissolve (c.f. accounts of the Maya pre much archaeological investigation and pre our ability to read their inscriptions for a particularly egregious example of this.) Now at Harrapa we find:

at least some Harappan residents were subjected to savage violence. The skull of a child between four and six years old was cracked and crushed by blows from a club-like weapon. An adult woman was beaten so badly—with extreme force, according to researchers—that her skull caved in. A middle-aged man had a broken nose as well as damage to his forehead inflicted by a sharp-edged, heavy implement. ...

But that's by the by. From the primal point of view what one would really like to know is what they were eating and what effect that had on their skeletal health.

Original paper: - International Journal of Paleopathology - A peaceful realm? Trauma and social differentiation at Harappa