Oh god I'm trying to remember the South Asian Societies class I took in College for my Anthropology degree.

The short answer is that between minor racial tensions that went back years you're talking about something that, similarly to how the middle east was handled in the aftermath of WW1, borders were semi-arbitrarily drawn with seemingly little regard to displaced minorities. Between India and Pakistan neither government made any real effort to safeguard the rights or protections of minority groups who left in droves, often feeling like second class citizens or outright homeless. The migration of millions of people hadn't been accounted for. Security was virtually non-existent, ergo rioting became reasonably common. When you have over 10 million people shifting between borders at the same time, and security is lean, riots are liable to happen.

Not to dump this entirely on the British colonial authorities laps though- the British had good reason to believe the colony was on the brink of civil war.

Wikipedia actually has a list of artistic depictions of the event- http://en.wikipedia.org/wiki/Artistic_depictions_of_the_partition_of_India

and while I wont speak to the quality of all of them, Train to Pakistan I can say was good, if fictional. The problem with facts when you're talking about over 10 million people is that something is always happening somewhere. Sometimes fiction tells a story that is more real than rote factoids.