First of all, don't believe all the numbers. Reading FII numbers is as complex as reading a chart.
Secondly, you can manipulate an index. You can buy some components, sell others and keep the index same. Or you can sell index, buy non index and hence bring down the index. I remember seeing some stocks which were up, although since most were down, I think this may not have been an issue.
The issue was the globe and while FIIs might be buying because of expectations of GAAR resolution, they probably got blindsided by global worries.
Still very hard to read tea leaves.
It is my observation that FIIs and DIIs go opposite directions, do maybe RBI / LIC or some other agency is doing equity stabilization work and hence some positions are always opposite if FIIs.