Hamas casualties estimated at around 1,000 killed thus far

This written piece from @Channel2News cites security sources estimating "around 1,000" Hamas men killed during Gaza operations.
— Jonathan Schanzer (@JSchanzer) July 31, 2014

I have no idea if this is accurate, but it's the first solid estimate I have seen of this sort. And would challenge Hamas figures greatly.
— Jonathan Schanzer (@JSchanzer) July 31, 2014

One other note. If this # is accurate, it means Israel took out roughly 10% of Hamas fighters. Our @Military_Edge puts Hamas forces at 10k.
— Jonathan Schanzer (@JSchanzer) July 31, 2014